Replacement parts before install

[Wasted Income]

I agree with brew. If you are itching to swap something out, the timing chain and oil pump would be my targets. Assuming you're using the stock truck oil pan and pickup, be absolutely certain that you use the red oil pump pickup o-ring (GM P/N 12584922). Seems it's hit or miss if aftermarket pumps have the correct truck o-ring included. The truck oil pans use a different o-ring than the cars, and has caused many a headache when a new motor goes in, and has no oil pressure on startup. Also be careful not to pinch the o-ring when you re-install the pump pickup tube.

In regards to gaskets, that is one of the best parts of the LS. I can't really think of a gasket on the engine that is not re-usable if not damaged upon disassembly. Everything is o-ringed for the most part. Intake gaskets are good to replace on an older engine since they do sometimes take a set and create a vacuum leak. I have never, ever replaced a set of valve cover gaskets, on any junkyard engine FWIW. Even the steel exhaust gaskets can be re-used, but for the price, I'd start with a fresh set.