This is based on the 63 manual and working with my 66 GMC, but might also be a held with yours. The channels front and back are held in placeby several sheet metal screws on the top and front which anchor the entire wing windoe/front chan assmby and on the rear by AFIK 3 pairs of med sm machine screws. While the front is pretty much self aligning, the ones on the rear should all be left quite loose until you have them ALL in and have checked for straightness by looking down through the window opening with a flashlight. Have you removed the wing window asmby before the window lift or have you wrestled the lift out without removing the wing asmby? If you've been wresteling it's probable that the lift mechanism has gotten bent in the process.
Rotsa Ruck
