My 1974 Cuda came with manual windows. I thought about changing it to power windows vs. keeping it stock. Eventually the power window option won out and I had the power windows installed.
I got a power window kit from Electric-Life. It is a kit that is specifically made for the E-body cars. The new power window brackets bolt in the same place as the stock brackets. I took the Cuda to a local stereo shop that did the installation for $170.00. They also replaced the door's window seals. They said that the installation was a pain to do, so I'm glad that I didn't tackle the job myself.
After the kit was installed and the window glass was adjusted properly, I couldn't be happier. Power windows on a car without air conditioning is a blessing. After the installation the windows seal really tight against the upper weather stripping which makes the car's interior much quieter on the highway.
The window kit does take a lot of voltage, so it is not recommended that the windows be operated while the vehicle is not running. A while back, I got a smaller diameter alternator pulley from March because I was tired of the Cuda's headlights dimming when the car was ideling at night. This pulley spins the alternator a little faster than the stock pulley and is a great complement to the power window kit.
If anyone is considering such an installation, I would greatly recommend it. Just remember the following: 1.) Replace the window seals at the same time. 2.) Make sure that your charging system is up to par