Hi drummin 52. I'm in the process of doing the exact opposite. 48 door no vent to 51 with vent. One thing I did notice about the 48 door which had the full pcs of glass. It has a built in channel that holds the pcs of rubber that seals out the weather right accross the full width. Now the 51 door stops short of the vent window. This means you will have to fab. & lenghtened the groove to accept the longer rubber. Remove the angle bracket that holds the vent & straighten the door skin lip. The window garnish on the 51 to 55 has a notch to line up to the angle bracket that holds the vent window, a small patch to fill in the groove is needed to make it look like the 48 to 50 door window garnish with single glass. I am by no means an expert subject just figured I would share these observation. Hope this can help. Good luck
