This discussion seems to be focusing more on making power than in being reliable when hard at work. Making power is great as long as you realize the cost and the consequences. The higher the power output, the more heat is created and the better the cooling system has to be. Bottom line is, "How much money ya got ta spend." If it's not much, spend it on the durability, reliability and cooling stuff. Do that and you'll be able to work the engine harder, longer. If you later can afford more power mods, the durability, reliability and cooling stuff will have the truck prepped for them. Personally, I think it's better to have a lower power engine that you can run flat out reliably for days on end than to have a more powerful one you have to worry about and back off. Sure, you can have both... if you have enough coin... but often you have to sacrifice a certain about of reliability (in the towing realm here) to get the power. There are guys out there with very powerful trucks who can't use the power when the going gets hard because they can't keep them cool. In the end, they don't get up the hill any faster than the lower power trucks.
In the mid '90s, I found a 100 GPM water pump for my 6.9L to replace the stock 80 GPM. It got damaged in '02 when I hit a deer and I wasn't able to find a 100 GPM replacement. I can't remember much about the 100 GPM unit. I got it from a diesel truck place in Grand Junction, CO. Maybe it was for a bus or something, but I just got a bunch of 6.9/7.3 material from Navistar for a story and all the bus and truck engines from 1982 to the late '80s had the 80 GPM unit. Anyone run into one of these 100 GPM pumps? Might be a help to those with high load situations. I noticed a difference with it!
Beware! Obscene Gasser Comments!
Having built a number of high compression, high output gassers and then put them to use towing in pickups, I would not recommend that to anyone. There is a reason industrial gassers have low compression ratios... combustion temps and pressure. When you increase the static compression and then use a typical "RV" or "Torque" cam, the dynamic compression is so high that eliminating detonation is just about impossible and even if you can somehow control detonation, the high combustion chamber temps are very ******* piston crowns and valves. If you put in a longer duration cam to relieve that dynamic compression a little, then you move the torque band higher and not always in the best spot for a tow rig. I built a 428 FE Ford for a guy that towed very heavy with a mid '70s Ford. This was the mid 1980s. It was initially built with a 9.6:1 CR, an RV cam with duration at the longish end in that class and all the other mods you would expect, Edelbrock intake, big Holley carb, headers, Accel distributor, hot ignition. Ran like a ***** ape solo. Pulled like a Clydesdale when towing. One problem. It pinged towing heavy on hills, even with the highest octane gas and/or best octane booster. And it ran hot. It would have soon destroyed itself. Fattening up the mixture didn't help much and neither did backing off the static timing, recurving the distributor or fooling with spark plug heat ranges. In the end, I had to eat the cost of decompressing the engine to around 8.5:1, installing a shorter duration cam and rejetting and recurving (for the 3rd or 4th time). It didn't run quite as strong but at least it didn't ping and the guy could run the truck as hard as he wanted up the hills without overheating or pinging... and on regular fuel too! He ran the truck about six months on the hi-comp setup and when I pulled the heads, there was already signs of piston erosion from detonation so I was glad I didn't let him run it any longer. This lesson saved me on the next truck FE build (a 390 this time) and that had a more satisfactory initial result. When I reflect on that story today, I would have paid more attention to gearing. This guy towed a monstrous (35 foot IIRC) 5th wheel. I don't remember clearly his gear ratio. It was no lower than 4.10:1 but I think it might have been 3.73:1. A 4.56:1 ratio would definitely lessened the load on the engine. Enough to stop detonation... I don't think so... but in retrospect I should have recommended a drop in ratio or a milder engine at the get-go.