I have rebuilt plenty of pumps for antique engines where commercially-built items were not available. Trust me on this- - - - -if an already-built pump is available, use it! The carbon/ceramic mechanical seal that's commonly used in water pumps is exceptionally fragile, (and expensive) and I've gone through two or three at times before one worked right. The really old ones with the gland nut and graphite-impregnated rope packing are a lot more user-friendly.
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!