318 or 340?

Can typically get a good running LA 318 for 150 bucks complete. 5.2/5.9 magnums usually run 350 bucks. Many of these you can pop in without rebuilding.

A little more work involved with the magnum (mechanical fuel pump and intake mainly). If going on the cheap skate side of things, more bang for the low buck with a magnum.
Enough good advice already been offered, I think the op can make a good decision according to what they want.