wiring harness interchangeability

[454Sub]

Originally my truck was a 90 1/2 ton 2wd with a 350/700 combo. It now runs a 454/400/doubler, hacked into the original harness. I have access to a 4wd 91 4l80e, with the entire donor truck harness and adapter. I would love OD. So my question is, can the factory 1/2 ton 90 harness be separated at the fusebox, and instead be partially wired with the donor trucks harness to tranny, and obviously replace with the donor truck ecm, and fusebox as well for the tranny fuse, or will entire harness have to be swapped?. Can anyone possibly give both pinouts an eyeball and see if this is possible. Thanks.

 

[paratrooper307]

Originally my truck was a 90 1/2 ton 2wd with a 350/700 combo. It now runs a 454/400/doubler, hacked into the original harness. I have access to a 4wd 91 4l80e, with the entire donor truck harness and adapter. I would love OD. So my question is, can the factory 1/2 ton 90 harness be separated at the fusebox, and instead be partially wired with the donor trucks harness to tranny, and obviously replace with the donor truck ecm, and fusebox as well for the tranny fuse, or will entire harness have to be swapped?. Can anyone possibly give both pinouts an eyeball and see if this is possible. Thanks.

Don't see why not, you can wire up just about anything with enough time and effort. However, since you have the entire harness, computer, and fusebox from the old truck, it seems the more sensible option would be to swap the harness to avoid hacking up your existing wiring even more, potentially creating a headache if it fails. The harness on these vehicles isn't overly complicated, seems swapping it over would be a wash as far as time goes, and you'd be eliminating your existing hacked harness.

 

[454Sub]

Ok, the fusebox splits into 3 clusters of wiring. Now, it seems to me, its basically headlights, taillights, and engine/tranny wiring. This donor harness is missing the headlights and taillight section, but mine are perfect, so that's ok, but does anything else run in those looms, like fuel pump wiring perhaps?, not 100% sure yet but I havnt found it yet. I really just don't want to get halfway through removing a good 400 and realize I regret it.it.

 

[dyeager535]

I would think one of the major obstacles would be the PCM vs ECM. Does the '91 PCM have the same terminals (not connectors) as the '90? If so you can depin/repin if needed, but if not, swapping the entire harness may be the better option. It's certainly going to be cleaner.

Have not dealt with the "E" variant transmissions, no idea how much, if at all, they were integrated into the firewall fuse panel connector. I would think little if at all?