Since you asked...............
I'd find the best engine guy/machine shop in my area to check everything about the block and rotating assembly to make sure a) it's saveable, b) they're the right parts, c) if they're WORTH saving. If all that can be done, and done economically, then make sure the flexplate is correct for that model engine/crankshaft. Not all Chev small blocks are balanced the same. I'm not that much of a chev expert to tell you which ones are internal balanced, and which are external, but I recall there are differences. Again, seek the local expert who can see and evaluate correctly, what you've got. Otherwise, especially with a Chev 350, a crate motor pencils out real well against a proper rebuild of a suspect engine. They have all sorts of choices, and most of your equipment aside from the shortblock will either transfer to a crate engine, or have some value, for example, on ebay. And they come with the General's warranty.