Go to swap meets. I found a 350 4-bolt main block, cast iron crank, rods and pistons for $100.00. I had to have everything machined, and I trashed the pistons for forged flat-tops + .030, and I ended up with a pretty nice street motor. If you want a done motor look at a GM Performance catalog and price a 350HO or a ZZ4 or a fast burn 350. Get out the check book.