Aftermarket A/C

[Puzzigully]

I don’t think they are difficult to source, but they are inefficient compared to a modern system.

I wonder if the inefficiency is in the compressor of the evaporator...or the whole system?
That is, would an original system be more efficient if you used a modern compressor?

It really comes down to what you are building, something that’s as you could order from Holden, or a car that suits your personal ideas.
Land cruiser utes have a thin ball freezer vent under the steering column that might work the way you want.

Great way to describe it