Do not use a Melling M55 on ANY race engine, and not wise on anything. They are not made like they used to be. Instructions in the box tell you not to use them with solid mounts. And as a second note, Melling no longer uses billet gears in ANY of there pumps, as well as what they sell to other companies. This includes their select and aluminum pumps. Only 3 companies to my knowledge use billet gears, CVR, Titan, and Moroso's gerotor pump but NOT their others. CVR is the least expensive and is well made. Here is some more reading on the subject.
http://speedtalk.com/forum/viewtopic.php?t=6868