98 gmc carb swap

[BigBlocksRule]

While you're wrenching and throwing $39 Chinese dizzy's on your engine, I'll continue to drive my 200,000+ engine that's had nothing changed but plugs. The one in my work truck is almost 300K, same thing. O'Reilley's and AutoZone will shoot codes for nothing.
If all the OP is finding is hacked up harnesses, he needs to find another recycling facility, there are plenty around here. A new harness isn't going to cost any more than a new carb. Then you've got to spend the coin on something to run that overdrive tranny AND you'll have to have a TPS on the carb. And a new fuel pump.
I understand the OP's frustration, but he does admit it has the wrong harness and computer - there's NO WAY that everything -O2 sensors, MAF sensor, etc. quit working at once. Take the time to eliminate the problems and you'll end up with a truck that'll get better fuel economy and will have some resale value.

There's a reason that everyone's gone to injection and gotten away from carbs!!!