What I've got is an 05 rcsb 2wd with 4.3 auto. And what going in is an 06 6.0 and 4l80. What r some problems that I will run into with doing this swap. I've heard that a 4.3 wiring in the truck is completely different? So if anyone could shed some light on this I would appreciate it. Thanks

 

I am also interested in this process. I have a 2000 GMC stepside 4.3 5spd, that I am putting a 6.0 into with a 6 speed. Not meaning to threadjack or anything but I think we can both gain some valuable info from this.

 

I'm buying a 99 GMC with a dead 350k mile old 4.3 V6 and auto. I haven't yet decided if I'll be doing V8 or rebuilding the V6 with a stroker kit and hoping for more power that way. It would be nice to know apx how difficult it is. From my limited reading on fullsizechevy.com it sounds like the 4.3 uses the same trans as the 5.3/4.8 with just a bolt difference on the bellhousing. Most accessories will swap over but you will definitely (of course) need the wiring harness from the donor truck along with the trans computer (of course) if bringing a new tranny in.