You can make 650 with out a huge cam on stock internals for a good long time (100K miles), But if you add forged rod and pistons to the mix you take out all chance of something breaking. (the crank can take way more then 650 (more like 800 - 850)
You can build it for less then 10K with new parts.
Here is one being sold for 12K pre-built
http://www.schwankeshortblocks.com/s...i=97380&c=1070