I purchased a pair of GT Factory Diablo Vertical door hinges for this project. These hinges were a strong, weld-in design to accomodate the heavy Firebird doors. My wife wasn't comfortably able to operate the doors from inside the vehicle when first fitted. This was corrected by replacing one of the 150lb struts with a larger 250LB strut (SPD-GS-3100-250). The required larger 13mm ball studs screwed into the same threaded holes of the hinge

as the 10mm stud it replaced.

After grinding off the upper door hinge, the body had to be cut away to clear the hinge pivot body. Once the arm is flat against the door and the rest of the hinge is as far inboard as possible, it was welded in.

They open horizontally a few degrees then swing up once the neck of the hinge clears an adjustable guide plate. This allows the use of the factory latching system. Each travel direction is adjustable by various screws allowing you to put the door where you want it. This avoids akward ingress/egress issues of some of the other hinges on the market I've seen.

Fenders had to be trimmed back to clear the door vertical swing. The mirrors were extended to fill in the gap.