First I searched and didn't see much on older trucks and swapping a LS1. And I couldn't help but notice this is really a great forum.

I have a 76 Cheyenne restored 30k miles ago, 400 SBC, 4x4, 400TH. Recently stripped her and replaced caps, rockers and door jams as well as rear quarters and hood. I don't think the paint prep was done properly on the restoration but the truck was used 2-3 years post restoration in lots of snow and ice.

Anyway no rust and nice truck that runs well with new paint now. Just needs some attention to small stuff like no CD player yada.

The 400 was rebuilt with the restoration and runs fine except the gas mileage is poor but duh. It needs a tune and the quadrajet may go away for a Demon. It does have a mild torker cam supposedly and has an aftermarket alum intake. Not sure what year the HEI is.

So I'm trying to decide whether to leave it alone, drop a 454 I rebuilt for street use in the last few months and get worse gas mileage, or swap out the 400 for a LS1 and get pretty good fuel economy. The motor comes with a 4L60E and I have another one sitting around.

Has anyone swapped a LT1, LS1, or LS2 into a similar older truck? What problems am I gonna have besides the harness problem? How hard would it be to put a new fuse box in and not rewire the body harness? What about exhaust? 4L60E conversion problems? Thinking of Dakota Digital instruments BTW.

Any ideas, thoughts, or opinions appreciated.