Are you referring to the video below?
If so, he did exactly what I did to my ‘77 which came with the dealer added ARA underdash air. I replaced the York compressor with a Sanden several years ago and it cooled but not well. Last fall, I pulled the entire system out.
I cleaned the evaporator, replaced the fan switch, and expansion valve, and cleaned the evaporator coils. I replaced the condenser with a larger parallel flow condenser, replaced the drier, and made all new nylon lined 134 compatible hoses for it. I got it all in, vacuumed it down, charged it up with 134 and I am getting -2 degree coil temps. It will FREEZE you out in the middle of summer.
After 6 months it has not leaked down a bit. You could do the same with any under dash system that fits. The key to cold air with 134a is a large condenser. You want the largest parallel flow one that will fit and you want a fan that will pull a lot of air thru it. The rest is just plumbing… I have a thread on here with some pics of mine.