I could not find this info listed anywhere so i thought i would post it; even though the parts fiches i looked @ showed different part numbers a v45 water pump will indeed fit a v65. I put an 82 V45 one on my 85 V65 so it would seem most years must have been identical. Anyone else have more info on the compatibility?
The V45 Water pump will fit the V65 engine, However, the V45 pump does not pump the same volume of coolant as the V65. the difference is notable if you look at the impeller size, the V45 is smaller. A V65 with a healthy cooling system might not have a problem with a V45 water pump until very hot weather and in slow city traffic.
Hope this helps.