I've got a '66 that had the two individual electric motors. One was missing and the other was fubared aftermarket crap. I bought a single motor wiper setup and modified my windshield to fit it. I like the two speeds and the fact that it doesn't have that SPAZ effect of two motors acting independently. Cost was less than two motors and its still TOYO.
Where are you located ? I know a guy in Washinton State that would probably have what you need. The only catch is he is cash and carry only. I'll be heading out there at the end of the month with a list of things I need. Picked up a spare wiper cable for me 73 on the last trip out.
Piece of cake once I had the dimensions, you can't use the same holes, either of them. I was at the assembly stage, so everything was painted, found some neat little vinyl plugs to close the old holes and drilled some new ones. No threaded holes where I needed them so I used some sheetmetal screws that have a drillpoint on the end, like the ones they attach metal buildings with, hexhead. Since I have the '66 windowframe, my WS is about 3-4" shorter than the later models that don't have the cowl vent in the WS frame, so had to cut, shorten and weld my wiper arms,PITA. It works and looks fine, IMHO