Hi, I have a '97 GMC Sierra Pickup with a 4.3L V6 Votrec engine. I spun the rod bearings and found a 4.3L V6 Votrec out of an '04 Astro Van. My neighbors installed it for me. The engines looked almost the same. we had to change a few things, like keeping the aluminum intake manifold from the 97 GMC, and we had to drill and tap a knocking sensor hole in the block to fit the origional sensor. But I think it's gone pretty smoothly. It's in now, and begins to turn over but wont start. I talked to a second mechanic yesterday and he says the 04 Astro Van engine will never work in my '97 GMC! that's the first I heard of that. I REALLY hope thats not true. Can someone help me out with this? Is there a year range of vortec engines that are compatible with only certain years? Thanks, Chris from Oklahoma.