1st 340 build
Just my opinion, but if you only have a block, you will be spending on parts and machining. If you dont want to spend on that, you have to buy a running engine and pay at that point... You need a 340 or 318 crank of some type, I'd get whatever rods to match the crank, and then buy KB hyper pistons. The block will need to be bored and honed if it hasnt benn, plus degreasing, etc.
You cannot cheap out by buying only a block. You'd be better to trade the block for a running 360. JMO...