[bigblockv6]

I converted to a fan clutch setup on my 68 KM-2500 and it has worked out well. Just taking a wild guess I ended up using an 88 Suburban fan with an 80's Caprice fan clutch and everything fit to the V6 like it was made for it. The distance between the fan & radiator as well as the diameter of the fan were correct. I'm sure it can be different on your 64 but you did mention Rock Auto has one, I can definitely say it's worth a try.