the vac. wipers in the '60 have vacuum boost that comes from the top of the fuel pump to assist when you are at heavy throttle. If this is just a cruiser and you are just worried about getting caught in the rain, I think I would try it first and see how slow they are. They will always work when you leave off the throttle kind of like intermittent wipers. I had a '60 and the wipers would all but stop when you were going up hill and as soon as you crested the hill they would go so fast you would think they would fly off. As far as 63 & 64 fitting I don't know. In 62 they offered a single speed electric with a 2 speed optional. Easy to spot a 2 speed as they all came with windshield washers. My guess is a 62 will fit as the wipers were opposing as compared to the 63-4 had parallel running wipers so all the linkage would be different.
