My pass side rear quarter has a lot of bondo and rust as well as the gapping hole in the lower window channel corner. Does the Goodmark full rear quarter panel cover the window channel area? If so I might as well fork out the $$ and replace it all.

It would help if we knew WHAT YEAR you were talking about. But full 1/4s do include part of the window channel.
Ron

Know also that the 3/4 panel will cover about the first 8-10" of the window channel. The cost difference of the 3/4 vs the full is a few hundred dollars, so depending on the size of the hole and if you need the sail panel, you might consider using a 3/4 panel and then welding in a patch if any of the hole remains...

car is a 70 and i have rust from lower corner all the way up. also rusting over into sail panel

The full 1/4 sail panel on the '70 (and others) goes up to about the narrowest portion at the corner where it meets the top. This will also contain the window channel on the side as well.