If you really want to buy my LT1 for your third gen, I still have the harness for it as well. It's better than Howell or Painless, made by Techrods.

I have had zero issues with it and went back to Techrods for my LS1 harness as well.

Let's chat if you want, but my suggestion would be to save the $ on spec carb parts, just run it as is until you are ready for the 5.3 swap.

Sean can give you lots of good advice on making the 5.3 work well in a third gen.