It shouldn't be that bad. Check out the last two pages of my Hillbilly Deluxe build thread. I wired up my truck with a 94 Explorer engine harness, 89 dash harness, pieces of my original headlight/horn harness and plugged it all into the 87 body harness.
I ended up splicing about 6 wires for the body to put the plugs for the rear lights and the fuel pumps on the 4.0 harness. The only pieces of the headlight harness I reused were the side markers and horn. The 4.0 vehicles had two different horns for the high and low note. The gen1 only had one unit.
Get your whole headlight harness from the donor vehicle and these lights from LMC.
http://www.lmctruck.com/scripts/mgrqispi.dll?APPNAME=WebLmc&PRGNAME=Welcome&ARGUMENTS=-ATK,-AFR,-A47-0282,-A/icatalog/FR/full.aspx?page=63
The bulbs that come with those lights don't plug into the Gen2 harness, but the bulbs that plug into the harness will fit those housings. It's not a perfect fit, but it is extremely functional. The front marker/turn sockets fit the gen1 front marker/turn housings that are down in the header panel.
If you look at the wiring books you will find very very few wire colors changed. I took really crappy notes on the wire-work of my swap but I will bet you dollars to doughnuts that if you are willing to put some work into it and we keep this thread going I can have you running, with all your stuff intact, on the first or second shot. We can even keep the older dash, you just need the wiring harness and a seam ripper. About half the plugs behind the dash are the same.
The hardest part of wiring in your dash is the instrument cluster. It took me two days to figure that out and about two hours to get the rest. Now that I have one working I can just pop my IC out and take pics of the plugs.