Is there any reason you're set on the 6.25" rods? It will not only slow down the reciprocating mass that you're trying to spin to 6500 rpms, but with that long of a rod, the compression height on the piston is probably gonna be less than 1.25"....which may cause you to have to put an
oil ring in the wrist pin hole. While this isn't a terrible thing to do, you'd be a lot better off without it.