HERE'S a thread on the Melling oil pumps.
The "Select" pumps are recommended by Melling for use in solid motor mount and/or high performance apps, whatever that's supposed to mean. To be safe, use the Select line.
Melling supplies their castings to others, so the problem is not just Melling-branded pumps. Other pumps to watch out for:
Melling M55
Melling M55A
Melling M55HV
Sealed Power 224-4143
Moroso 22100
Moroso 22135
Canton #21-500
The sheet below is what's supplied w/the standard-type pumps:
