Chevy & GMC Vans

Hello fellow g vanners. I have 89 g30 starcraft with a 6.2 and th400. I also aquired 93 g30 starcraft with a 6.2 and 4l60 for parts since the body is too rusted away. I would like to take engine and transmission from 93 and put it to 89. As far the engine and transmission itself it should be pretty straight forward swap. But my question is how much wiring i need to swap. Do engine and transmission have separate wire looms or do i basically need to swap everything including cabin? Thank you in advance.

Welcome to the forum.

I would swap everything. But what's wrong with the '89 engine?

I want to upgrade gearbox 3 speed th400 just wont do it for me. And i can just replace th400 with 4l60e without doing the swap

I did a swap, '93 g20 350 CI into my '93 safari to replace the 4.3. IIRC the g20 wiring was identical to the safari in that the computer was engine and trans only not into the cabin. There is a bulkhead connector behind the battery of the safari that does the fusebox at the driver's feet that I did not swap.
I would recommend getting the factory service manuals for both vehicles for reference.