Well, thank you all for the responses, and Happy Easter! I Suppose I should answer some of the questions asked of me here.
1)IP: The Injection Pump is a reman from Stanadyne, and has a Stanadyne badge which is marked "Remanufactured".
2)Mileage: I know the truck has 120k, and not 220k, because the original owner, who screwed up the wiring, took otherwise excellent care of this old beast. He wrote down the date and mileage of every oil change up until he sold the truck in 2009, at which point it had about 98k on it. I bought it in 2013 with X14,***.X miles on it, so I doubt it got over 100k miles put on it in about 3 years, which took 22 years to reach previously, especially if it was only making about 10mpgs!
3)Tires: Tires are 235/85-16. I was an OTR truck driver for a while, so I'm keenly aware of tire pressures. The drives are filled to 80 psi, and the steers are 55 psi (door specs are 80/51psi), filled at a truck stop, checked with my trusty gauge.
4) IP Timing: I bought a Snap On MT480, which came with the Luminosity Probe for $150 on Ebay. It came with the remains of the original box, instructions, and the meter itself looked like NOS, barely used. I cannot, however get the damned thing to give me a reading. The RPMs fluctuate wildly at times, and the top needle pegs to the far right as soon as I connect it to the terminal. When I re-installed my IP based on the fine instruction tutorials provided by numerous fine folks online, I am certain that I did it correctly. After the re-install, the IP was timed to the timing mark, and then...
5) Smoke: I would say that I have very little smoke. When I started the truck at the timing mark setting, I had a very small amount of white smoke, which I believed indicated incomplete burn. Thusly, when I would put the hammer down for brief road tests, it would expend white smoke, according to my buddy who was there on the ride along. I then advanced the timing slightly, about 3/32 worth, until I got black smoke during the same. The truck felt a bit more responsive (marginal) but my long term road tests netted horrible MPGs, which is why I'm here. Should the truck ideally produce NO smoke at all for best efficiency? I know Diesel fans pride themselves on their ability to "roll coal", but I am too cheap to be concerned with impressing or annoying anyone.
6)Driving: I really do drive like an old lady. My commuter car is a 97 Toyota Corolla base model with a 3-spd auto, 224k on the clock, and I get 37mpgs on it all day long. Personal best was 39.8mpgs, tank average. I drive that an hour to work everyday at 60mph on the interstate. I got used to being passed when I was driving rigs, and now I don't care about putting anyone in their place, and this car couldn't do it anyways. The truck is arguably less responsive than the car if for no other reason than sheer mass. Trust me when I say I drive it at 55mph on the highway and get 10mpgs, I'm not driving it like a teenager for that to happen.
7)Transmission: The C6 is a marvel of reliability, but I have wanted to dump it since I figured out it only had three gears. My old 2003 Mercury Marauder (which I sold, despite my undying love, because it was bad on gas!) had a 4-spd, which I thought was pathetic for a car built in the 21st century. My dream is to find a junked out F-series with a Gear Vendors six speed in it, but I apparently have bigger fish to fry before I worry about that.
8)Odometer: Accuracy was checked with a GPS AND my Smartphone GPS. I was shocked to discover that with these factory sized tires, the speedometer was within +/- 1.5 mph, and the Odometer is accurate to within about 1-1.5 miles. This truck was sold originally to a person who lived in the same town that it was built in, so he might have known something about this tire size. It is more accurate than any other vehicle I've tested in those two metrics. The Corolla, for example, has a speedo that's off by 4-5mph with the factory sized tires. The fuel gauges, however, are guesstimates. I go by a full tank in the front, and my Odometer. I tried using a GPS tracker on my phone, but it was too difficult to remember to turn it on and off everytime I went anywhere in the truck, wait for it to initialize GPS, hope it would never crash, etc.
9) Brakes: The rear brakes were non-existent when I bought this thing. They would lock up, and were softer than a new pillow. I put a new hardware set on the rears and drained the entire brake system with a vacuum pump. They're now much improved, and I don't think they're dragging, but I will try pushing the truck on the street to see if it rolls very far.
10) Bulk Weight: I have cut off the stupid, idiotic spare tire mount on the bottom, which took me around 2 hours of unscrewing and messing around with it, which should have reduced the weight by about 80lbs. Damn steel rims weigh 50+lbs. I would like to change those out for lightweight aluminum ones when I get the chance, just to improve my City MPG if for no other reason (but aesthetics are a big reason, too). I don't keep too much in the truck.
11) Aerodynamics: I took my CB antenna off (and promptly lost the little plastic insulator for it) and don't have much in the way of drag inducing items. When I heard these trucks could get 20+mpgs running WVO and B99, I dreamed of putting belly panels and an aerotopper on the back to be able to hypermile with it. Getting 25mpg with an ancient truck just to **** off people at the University I work at would be fantastic, but seems unobtainable at this juncture. "My truck is greener than your Prius, hippy."
12) Injector testing: I asked the folks at Pensacola Diesel to test these when I was buying them. They, along with my local Diesel Mechanic, both said that it was unnecessary to test Delphi injectors, as they were usually high enough quality that most companies that said they tested them had a larger variance than Delphis did from the factory. This was two different people, in two different parts of my state, who know more about diesels than I, only one of which had a vested financial interest in the advice. So, despite what I had read online, I did not bother to have them tested. I also changed the return lines, O-rings, and caps (which I then changed back, because the new ones leaked badly), and tracked down all the leaks I could find to try to get better MPGs. I do not think I have any serious enough leaks to warrant a loss of 1mpg, letalone 5-10mpgs.
13) Warm-up: I will say this truck gets HOT when I drive it. I drive it on the highway, and it's getting to nearly 220 degrees after a run. It's warmer under the hood than my gassers ever have been. This is one reason I wonder if it's getting too much fuel. All that unburnt fuel might be going into the exhaust and burning in there. I do have the awful, awful stock down pipe and exhaust setup.
14) THANK YOU ALL SO MUCH FOR YOUR HELP AND INPUT!