Hey guys. I’m swapping a 350 Vortec into my 95. Trying to plan ahead with the exhaust work, where do the O2 bungs need to be located? Obviously, upstream and downstream of the cats. But, is there a certain distance? Should an exhaust shop know these answers? Any help would be greatly appreciated.

Also, I’m looking at ordering a holly painless wiring harness to make things as simple as possible. Any suggestions or thoughts on that aspect would also be greatly appreciated.