All of the gen III engines are interchangeable. The only differences are the accessories. As long as you use the truck accessories it will bolt up fine...except for one bolt on the alt bracket--no problem not having that. Your 5.3 pcm will work, but it will run alot better with a tune. The coil bracket *may* be different though, I'm not sure. The 5.3 heads will up the compression to about 10.8:1 or so, but the intake valves are smaller unless you work the heads first.

 

what kind of times can I expect I run a 15.6 with my 5.3 what do you think the ls1 would do for me stock?

 

The one bolt that wont go in is an A/C bracket bolt as i understand and it wont hurt a thing to go without it.