I take a stock volume melling pump, bore the inlet to 3/4 and then use a Milodon pan/pickup and cut the end of the pickup tube off and weld it into the pump making the inlet a true 3/4.
Then bore the outlet to 1/2 and port the main cap. That's about all you need to do for most anything running under 8000rpm.
Make sure you have ample rod and main bearing clearance!
Brian