I have a extra ls3 throttle body from a friends vette he wrecked an parted out, I heard stock tb on nnbs is 87mm, so I be able to get a tb gasket for a 90mm an put it on an work? I also work at a shop where I have access so a snap on scanner that is able to do the tb relearn if needed but, besides that it should work right? Or is there another underlined issue someone has ran into when doing the swap

 

Should be a direct swap. Seal is on the intake, so none needed.

 

Actually you should let me buy it... you'll never get it to work

 

A waste of time for a stock 5.3, I tried it a few years back.
plus you need to change the size in the PCM so it makes
the right A/F ratio. a relearn not needed. just pull off the neg batt cable
for a while.