Yes, with one caveat thrown in: Part numbers do not seem to be copyrightable. So you have to make sure that the part is advertised as a Melling M63HV and not just a M63HV oil pump.

Looking at the Ebay Pep Boys ad for the pump they clearly state Melling and so it should be okay.

About a year ago I was buying some NGK plug wires for my Hyundai. The NGK part number is either XX90 or 7962. They are blue in color.
I found the lowest price on Ebay and ordered the 7062 plug wires. It had been a long day and I wasn't paying attention. I focused on the part number and the price which was lower than any other. When I got the wires they were indeed blue, marked with the right part number but I'd never heard of the brand before.
I found the original ad, and sure enough they called them everything but NGK!

Lately also I've run across thousands of suspension parts that have MOOG part numbers but aren't MOOG. They are not labeled as MOOG, and so one has to be really careful. There is also a BRAND NAME "OEM Parts" but they are not original equipment.

R.