65 Barracuda Quarter Window Question

I just came in from the shop after wrestling with my quarter windows. Is it even possible to get the window track on the regulator with the regulator still in the car or does it have to go in place as a unit. There just doesn't seem to be enough room down there to get the track on both regulator tabs. I've tried about every position on the reg to try and get the track on but it's like about a half an inch away from being able to get the second tab in the track.

Thanks in advance for any tips that might make this a bit easier. My back's getting damn sore from peering down into the front of the quarter trying to get this thing together.:x