i dont know about the water pump, but you should get a new one anyways, do not use the flywheel/flexplate as it is balanced for the 4.3 and not the 350, but you should be able to use all the front end stuff like brackets and pulleys and whatnot
well the 4.3 is already running in a truck and iv got a gm vortec crate 350 and i was just goin to use the water pump and all the brackets and stuff off the 4.3 if i could cuz it was all still good and i knew u could transfer the 4.3 parts on a older 350 but i didnt know about a newer vortec 350
I think the flex plate will work, but you might check part numbers on both at a parts store or online and see if they match. A friend put a 355 in a first gen blazer 2wd, and used all the 4.3 stuff, just used V8 intake and dist. Used firebird exh manifolds. Looked pretty much like it came that way.
New 350 and old 350 blocks are pretty much identical. Are you talking about an LSx based engine or just your every day 350. The only real difference with the vortec is the heads.
You can use a 4.3 water pump but I will agree with maverick and tell you to get a new one. They are cheap and better to do now than when it starts to not work. I had to modify my power steering bracket from the 4.3l because of using headers. I say modify, basically just cut a portion of the bracket that mounts to the front driver side exhaust port. Everything else bolted right up. Make sure the water pump has the proper flow for a serpentine setup.
I have Vortec heads on a '79 block and all the '79 brackets bolted back on with no problems, so, as far as the smallblocks are concerned GM kept the same bolt pattern. The thing I'm curious about is if the harmonic balancer is the same from the 4.3 to the 5.7