Great Job. I haven't messed with the book thing.One warning... on early models with the two speed radiator fan, you will either loose the two speed setup or have to mess with the wiring more to keep it.
Looks like 88 also used a differnt style fan relay... that's good. The older ones are fairly delicate and not really very weather resistant. (Another what in hell were they thinking item.)
If you mark the hood/hinge with a bit of paint or an obvious scribe line, you won't have to fart with hood adjustment much. Match up the marks will usually get it. (You can do the same with the HL lifts if need be. Usually you can line up the hardware with the marks it leaves on the lift.)
If you take the hinges off the body instead of the hood you won't need to mess with the headlight doors at all.
For reference... the spot you undid to flip the light up is the same spot I recomend people disconnect to make lamp changing allot easier.
Only the 88 harness might be short the one horn connector. Folks want to check the 88 harness as early ones could possibly have the missing horn plug tho it could be burried in the harness. (I think someone else recently used an 88 harness and said they found both plugs. Or at least they were told it was an 88 harness. An 87 harness will definitely have both horn plugs.)
This answered questions I had about how the front wiring works... The lighting harness is separate from the heater/AC wiring like the tail light harrness splits from the engine harness at C500. (C100 is one of the very few plugs I haven't had a reason to mess with yet.)
The plugs on the module are MetriPack weather resistant type. Besides potential clearance problems some folks mentioned... I'd have to worry about water there myself. The MetriPack stuff takes occasion drenching fairly well but the module will have allot of water and in winter snow and ice dumped on it there.
I don't know about if it will have clearance for the wires... but right next to the fan relay might work... It will still get plenty wet but that might cut down on stuff sitting on it and having a chance to soak in.
If it's not already... I'd recomend unplugging and giving everything some dielectric grease. Work out the back seals, assuming this is bog standard MertiPack with soft wire seals, and work a little grease into there and push the seals back in.
Why GM chose the location they did I couldn't say. It does keep allof of crap away and hides the module. Probably felt there was some sort of benifit durring assembly as well. I would have put it somewhere in the spare tire/storage area myself. There were several places in there they could have used for it.
As much as the OE location is a pain in the ass... The modules are pretty reliable and the odds you'd ever have to mess with it again are low.