The rotating assemblies in the following link are all for 1 piece rear main seals. They are 4.25" stroke. Typically you may have to grind a few reliefs along the pan rail to clear the rod bolt heads and maybe on the bottom of the cylinders with a 4.25" crank. There are a lot of 4.25 cranks in stock blocks.
http://www.cnc-motorsports.com/category.asp?CtgID=9260
http://www.cnc-motorsports.com/category.asp?CtgID=9260
