Headrage,
I just rebuilt my 2.7 myself. The prices quoted by Jim Sims are accurate. If you are unsure about rebuilding your own engine, I'd check out Supertec:
http://www.supertecperformance.com/engines.phtml
Henry lists a 2.7 long block for $7200 - less if you can re-use your old cylinders and pistons (I did). And you get a 2 year warranty which includes no leaks.
Just consider both approaches (DIY or Professional), and be realistic about your abilities and what you want to end up with after spending this kind of money.
Rex