Does anyone make a reverse flow water pump for older blocks, say a 75 350? Would there be any benefit to putting one on a regular flow system? Thanks

 

Are you referring to a reverse rotational pump for a serpentine/idler setup? A serpentine setup makes the water pump rotate the opposite direction of a conventional v-belt setup. It will bolt to the block just like a regular one. But if used with a conventional belt setup, water won't flow through the system, and you'll have a catastrophic over-heating problem.

 

If you are talking a system like on the LS engine, I don't know of any. There may be benefits if you could do it, but the plumbing would be a nightmare.