[rbgray1]

Be very careful with removing the door cutouts prior to permanently mounting the body and doing final door fitment AFTER the body is secured permanently in place.

The rocker / Sill is not a very strong portion of the body and can easily crack if the cutouts are done prior to body fitment.

One thing about fiberglass is that it will "relax" or sag over time if not supported. Since I am rebuilding my car, I cut two pieces of 3/4" plywood and fastened with many screws around the door frame area BEFORE I removed any body mount bolts and lifted the body off the car. I also build a rolling jig out of 2x8 framing lumber with casters and support from the body jig all or the locations that are supported by the frame. Due to Fiberglass tendency to "sag" over time, if you don't do this the body will sag and warp if not properly supported.

You have a slightly different issue where the center of the body is higher than the front or rear. I would recommend to NOT cut the door blanks out but rest the body in place on the frame, potentially attached to the front of the frame by the front frame rails, block the rear of the body slightly higher that the desired final position, maybe two inches or so, and get your workshop warm for a few days and see if the fiberglass "sags or relaxes" in the center section over a few days in a warm shop. You will be surprised how much fiberglass will move if you allow it to just relax into position.

If it does sag to where you need, you can follow remaining body mount procedures, complete the door cutouts and then refit your doors AFTER the body is permanently mounted. Ive seen where some of the members have painted their bodies OFF the car and then performed refitment of doors, hood, decklid. This can be done but you have to be extra cautious in properly supporting the body in the correct places so the fiberglass doesn't relax or sag in the wrong way.