Relays for switches
Just a couple of thoughts on the switches - these Dorman switches look like a good option as an alternative , but they are probably only designed for low current switching of a relay, not switching the full power to the motor and may burn out if used for full current switching.
Also on the 2600 sprint it is easy to blow a 10 amp fuse when closing the windows as there is no reed switch to sense when the window isfully closed or open . So if you keep pressing the switch the current goes up until the fuse blows.
I read somewhere that the last sprints had overload fuses/relays which could be reset after an overload. So with these Dorman switches I suggest you fit a relay with a 10 amp current overload ( the old motors still need the max power you can give them to move) with a 5 second reset after overload.
This problem is common on these Ducellier switches ( French electrics in an Itallian car!) and the same switches appear in similar era Ferrari's. Iso's etc . So are now very pricey. But there is a lot on the Ferrari forums on replacing switches and window motors with Ford units if you need it.
Then you have the fun of different wiring to different window motors depending on age . You can see the mess I got into on this post - after 3 days work the windows did both work for a day ! When I sold the car one did down and the other didn't work atall!
http://www.alfabb.com/bb/forums/1900-2000-2600-1950-1968/157421-operation-save-sprint-6.html
Ian