In my 51 Panel,
I just installed the "Specialty Power Window" kit
that is set up for AD Chevy pickups and panels.
It cost a bit more than the no name "universal" kits, but has vehicle specific instructions and diagrams for our trucks
The hardest part is trimming the window stop bracket that is down inside the door. (hard to get at!)
This must be done to provide clearance for the full "window down" position.
I used new glass and channels from Jim Carter and replaced the rotted window channel brackets that run inside the back of the door (from Chevs of the 40's).
WIth all this new stuff installed I found that the windows fit a bit too tight when buzzing up down in my trial fittings. I'll either try a different thinner style channel on the rear bracket, OR, have the glass shop shave the sides of the glass down an 1/8 of an inch or so. The window kit calls this out as a possibility when replacing everything with new stuff.
High quality kit and made in USA.
Mike
"Squire"