I have put a 1991 S10 blazer 4.3 into a 1987 S15 truck that had a 2.5. I have changed the wiring harness and computer in the engine compartment. But I have no power going to the computer and the main ground wire for the wiring harness has power coming out of the fuse box. And I am sure there are other issues that I have not come across yet.
Any input on what I need to do to correct these issues would be greatly appreciated.
I am hoping for an answer besides having toorewire the whole underside of the dash.

Thank you Rick

 

did you completely swap everything over and hook it up exactly the way it was if you swaped it out and only took certain things then that might be something to look into but on the other hand you said you have power from the fuse box out which means you have power in k do you have the ignition hooked up to it for turn key if you do what does it do? if it does nothing then check your ignition wire to the starter and your power to starter if anything you might have to do a rewire just to clean it up and get it right.