Ok I have a 2007 5.3 with no harness, computer or throttle body. Motor has an LS2 intake, injectors, 243 casting heads and a mild cam. My question is would it be worth the time and money to try and find a harness, computer and electronic throttle (Also would I be able to get away with everything from an 06 as 07 stuff seems rare)
or

Just go stand alone with a cable throttle?

 

I'm new here and to the LS motors, but your 07 5.3 should be able to use the MSD 6012 LS2/7 box and harness. You could use a LS2 carbed intake also with a carb or elbow with TB. I think most of the 5.3s use the same heads as the 6.0s but with smaller valves and combustion chambers. I just picked up a 2008 5.3 and put it in my wife's 2000 Yukon XL (just finished it yesterday). The heads are the same looking as my 6.0 Ls2 but the casting numbers are 799. Rod

 

I´m in the same situation but with a 6.0 LS engine. I was tinking in getting a harness from Speartech but I do have many doubts of what to do.

 

I just talked to John @ Speartech and am pretty sure he's got it figured out for me

for Speartech!