Re: removing the upholstered engine bulge; there have been a number of articles in the POCA Newsletter on performing this Gr-3 mod. As most know, the rear upholstery panel is a lightly padded leatherette cover over a sheet of fiberglas, and on some cars, it's difficult to remove it from behind the seats, to access the steel engine 'door' and then the engine. But if you break a vee belt or need to fix an A/C compressor or water pump leak, that's what you (or someone) must do.
To make the bulge removable, it is separately upholstered from the rest of the panel. On the backside of the big panel are two rows- one on each side- of tiny metric nuts, usually rusty and/or frozen. They are on studs welded to two narrow steel strips that hold down the upholstered edges of the bulge. You won't be re-using them so don't agonize over breaking one or two in removal.
By pulling back an inch of leatherette around the edges of the bulge, it exposes the underlying fiberglas. SAW the fiberglas bulge free on three sides so the bulge comes off intact with its separate leatherette upholstery still attached. A fine-tooth wood saw works well; cut straight! Tuck & trim the bulge's leatherette around the now-exposed edges and use glue on them instead of the steel nut-strips. A black Sharpie colors the exposed cuts on the big fiberglas piece. They will be more-or-less invisible or you can glue narrow extra strips of leatherette.
Screw the big panel back on the firewall, and use small pieces of Velcro on the backside of the now- separated bulge and the steel door, to hold it in place. You now have the factory Gr-3 street-racer-mod and no longer have to pull the big upholstered panel for access to the engine. It looks stock. As an added benefit, when you return the large fiberglas piece to the car, you can stuff chunks of 2" thick-fiberglas building insulation under it, trimmed to size, without having to glue it down since the upholstery no longer ever needs removal. This quiets engine noise better than stock, at very low cost.