There used to be some street rod suppliers which had electric window add-on motors for sale. A box (motor and switch) which fit over the existing crank handle spindle to do the deal. Not nearly as clean as the factory power window stuff, but still workable. Not "production-based" either.
Certainly anything which is done on the assy line can be done "in the field", BUT also remember you'll also need to modify your door panels (metal support surround clips for the switch to snap into, plus cutting the holes for such). In many cases, the location of the switches might not be similar to the placement of the window crank, by observation.
The space inside of the door shell to remove and install window regulators CAN/IS quite cramped, by observation. Not nearly as simple as it might seem, by observation, UNLESS you might have done it before and know how to move things around to gain clearance to get things out and then back in. The FSM can help, but "work experience" is better.
Power windows can be a neat thing to have, BUT the possible best way to do it would be to get complete door assys and swap the doors, rather than just the regulators and such. The doors will have the necessary wiring harness in them, plus the harness protectors (think "door to body"), plus any other minor things you might need to do the deal. AND, with the doors "being there", that would also mean any main feed harnesses to the power window switch should be there too! Not to forget all of the wiring that goes from the main switch, across the car to the passenger side of things to run that side of things, too!
By the time it's all done, it can be fun to have working power windows, BUT is it really worth it? Might be better to carefully remove the door trim panels and related watershield, wash the regulator mechanism with some spray cleaner/lube, and then put some quality non-drippable lube to the gears and linkages on the window mechanism. Such that the effort to operate them is much easier. THAT can be a significant improvement, usually. THEN you might realize how easy they should have been to operatle, all along. Plus how many turns it might not take to fully raise and lower the glass (think about 2.5 turns on the '65-'68 C-body cars).
Many side issues rather than just swapping the regulators themselves.
Just some thoughts,
Happy Holidays!
CBODY67
