Yes, oil pumps are rebuildable- - - -as long as the main body and the base plate aren't badly scored. It's also possible to adapt a pump for the 194/230/250/292 engines to work on a stovebolt engine, but it takes some pretty creative machining. Melling still makes a good quality aftermarket oil pump- - - -M-29 for the 54/55 engines, and the M-45, I believe, for the later 56-62 engines. Air in the oil stream isn't caused by the pump- - - -the pickup screen and associated parts usually create that problem.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!