If you want a 4-bolt main Windsor, you can buy them from SVO Ford
http://oemfordparts.com/partslist.asp?CategoryID=12
Part #: M-6010-S351 cost about $1700 US.

A cheaper alternative would be to use a stock block with a "main cap girdle" which ties all the main caps together to prevent "cap walk". This setup will easily handle 7000 RPM.

RCC