OK. I just did this earlier this spring on my 88 C-6. The only Left Handed Thread you will encounter on this is the large 30+mm "nut" on the fan clutch itself. For me, this was the worst part of this repair was getting the clutch loose. Having a helper was almost a must for me to get it loose and tight again.
For me, I removed the fan clutch, the fan shroud, the brackets that holds the power steering pump, and A/C Compressor on the drivers side. I just moved the pumps to the side, I didn't disconnect the lies to the pumps. Had to remove the brackets that was the adjuster for the alternator. The vacuum pump and alternator stayed mounted, just pushed to the side. Just to be safe, I laid the new water pump on the work bench and as I removed each fastener, I put it in the same hole in the new pump, so the same bolt came out of, and was returned to the same hole. My new pump cam with 2 new top bolts, which I used. The upper boss on some pumps is thicker/thinner, so they supply the correct length of bolt so you don't get the bolt into the timing gears. Once I had the old pump out, I moved the bolts back to the old one, in the same holes to keep them in the same position.
I also bought two 5/16 studs a couple inches long (or bolts and cut the head off) and thread them into the top two center bolt holes to act as guide pins. if you haven't changed an IDI water pump, they are surprisingly heavy, like several pounds heavy. I put just a very thin layer of schmoo (RTV) on the gasket, and slid the gasket, and then the pump on the guide studs. Threaded all but the two top fasteners into their holes, making sure to put the mounts back in where they went. Once I had all the bolts finger tight, I removed the studs and replaced them with the supplied bolts. Make sure to put schmoo on these two bolts, and the bottom two middle ones (when you have the pump off, it's really clear which four bolts) that pass through the timing cover into the oily side and will leak if they aren't sealed.
Put everything back in the reverse order. For me being a first time on an IDI (I've done water pumps on other engines before) it took 4 or 5 hours, just working through, not rushing. The most time consuming was getting the clutch loose (had to run back to the part store for additional tools)