Ive got a 2bolt 350 bare block that was given to me. Im getting ready to build this motor, and one of the questions I have is what to do about main caps? The block didnt come with any, and I remember reading years ago about how the caps and block wear together, and if you tried to replace the caps, it would lock up the engine....

The motor will have to go to a machine shop to be line bored with the new caps. not very expensive and a good idea to have done on an overhaul anyway.

then I take it that I can use main caps off another engine?

then I take it that I can use main caps off another engine?

you can or you can upgrade to splayed 4 bolt caps

+1 to both replies above.
Reply 2 does require more money, so you do need to look at how much power you'd like to make. Stock, stay with 2 bolt caps. 400 hp, go splayed. 600, go aftermarket block. ;)

Talk to your engine rebuilder, he likely has a 2 bolt block to sell you for less than the machining operation to reinstall the caps on your block.

A line bore cost me about $50 to do a 4bolt main block.