mellings pushrod for magnum heads?

If the Melling pushrods are the same 7.625" length as the Mopar Performance ones they are likely a little short especially if you have had any decking to the block or heads. You would be better off mocking the engine up and ordering custom length pushrods.

Regarding lifters most after market ones have provisions to oil through the pushrod and the same one is listed for AMC and mopar applications. It's just that if you order for the AMC application you are sure that you won't wind up with true mopar lifters that don't have the push rod oiling provisions.