Yeah the guy I talked to (he may be wrong), but he said there is a O2 on each downpipe on the y-pipe, then one in the end of the y pipe before the cat, and one after the cat. That sounds like overkill.
Those 4.3'* are 300K engines.......A buddy of mine had one, that thing was a trooper, it was overheated I dunno how many times, beat on to the point of blowing a spark plug out of the head, and it would always run like new lol.
Yeah, they are a freaking rock. My dad had the "first" year of the 4.3 in his '85 Chevy van with a 4bbl carb. The carb had a crack in it, shot vacuum hoses, but yeat the sucker ran no matter what. we finally sent it off the the scrapyard at 242k, and the original 700r4 and everything was still good, along with the engine, he just couldn't afford the $400 replacement carb at the time.