/6 water pump???

Did you get a w.p. yet, or just looking at photos? There might be 2 gaskets stuck together. If not, somebody needs to tell the Chinese or their middle man.

Re which w.p. is better, I agree w/ Dan in the slantsix.org linked article. Similar discussion for small blocks. Engines w/ AC got a 6-blade pump and non-AC 8 blades, so people ask "isn't more blades better?". Can't imagine they wouldn't use the optimal #blades for both engines, since almost cost-free. Most people decided it was because the pulley diameters varied between the two, so has to do with the speed the w.p. turns. Now for radiators, they did go cheap on the slants, making the core narrower to save copper.

"I was always under the impression that the A/C pumps had less fins on the impeller specifically to move coolant slower so it would pick up more heat while in the motor. By product of that was less cavitaion."

Above statement in the link is interesting to me as an engineer. Always bizarre theories about heat transfer, fluid flow, and thermodynamics bandied about by auto hobbyists and mechanics with no education in the subjects. Less water flow thru the radiator = more cooling? No engineering textbook covers that theory, and I don't even see the "common-sense" behind it. A Robertshaw engineer tracked down the source of that common "add a restrictor plate" suggestion on hobbyist sites, if you care to search. Spoiler alert - it started from 1930's cars w/ weak radiator cap springs.