switch 3.2l to 4.3l gm

Im jut curious, ive been having some problems with my 3.2l 94 rodeo engine. Just had the heads done and now it wont start. its getting fuel and spark, so im a little puzzled, but think that the timing belt may not be on right. if anyone has any ideas, theyd be a great help. But anyways, i was wondering if it is possible to convert to the gm 4.3l v6? I was wondering if it would fit, what the tranny differences are etc... Just an idea i was pondering. I am hoping to get the 3.l to run again, cause i loved it when it ran, but am getting a little tired of the price of repair parts for it up her in canada. anyways any ideas or thoughts would be apreciated. Thanks, Dave.