Adding ac to my ‘67 Dart

I put a 73 in a 72. Cut out and replaced a bit of the firewall so the 73 bolted in. It all just bolted in but I have yet to get the 73 system to work with a damn. It seems like the evaporator is being starved and the superheat is always wrong. Have a 68 Coronet and 66 Valiant that freeze you out. I recently learned that the 73 evaporator is a part year only design. It was changed in late 73 and stayed the same till 76. That partial year system does not have aftermarket replacements. I am believing that the 73 design is flawed. I have a 74 box with the newer evaporator design I plan to hack in for test this summer. My recommendation is stay away from that unicorn 73 design.