i have a 91 rodeo with the 3.1 its a daily driver that has a speratic knock to it so i was wondering what it would be to put in the more common 3.2 in it any advice would be helpful

If your referring to to the more common 3.2 Isuzu engine it would be a real challenge that engine is totally different than the 3.1 GM V6 that is in your Rodeo but if you meant the 3.4 GM V6, that is a very easy swap pretty much a bolt in operation. There is a lot of information on this over at Planet Isuzu forum. I did a 2.8 to 3.4 swap last year in a 91 Trooper and it was very simple job no hidden surprises no major changes. The biggest mod is drilling the block for the starter. Your 3.1 has a lot of potential. Have you looked at Betterthanyou's web site? It has a whole write up on performance mods for the 2.8/3.1 V6. Goodluck DAVE