Got a chance to get a 400 block and a steel 350 crank to use in my 65 chevelle, its mine for free if i want to use it... anybody have any experience with this setup and what kind of power or problems associated with it?

You'll need bearing spacers for the mains.

Less common than the 350 block/400 crank 383, so be careful about rod and piston selection.

Can make good power, but I'd prefer the 400 stroke crank.

No real "problems" associated, but you need to be careful that the block is usable, & the heads and head gaskets have steam holes drilled in them. It would be common to use the internal balance damper and flexplate/flywheel, but of course you'll have your machine shop balance the engine.

For free, well, go for it no matter what. I'd go for a 400 stroke crank as well if I were you, perhaps sell/trade the 350 crank for one and go with a full 400ci motor.

Cant beat the price.