I installed them on the GM rails, and kept the original electric operation.
You have to mount them as far back as possible. A welded square frame that bolts to the OEM rails with studs, and the bottom of the seat with socket head cap screws is a nice solution. I would use angle stock for the side rails that bolt to the seat, and bar stock for the cross rail pieces. The vertical side of the angle stock would be inside the seat screws, outside of the rails, and be oriented downward.