Here is what I did on such a project. I matched the old condensing unit to a new copleweld condnsing unit, then replaced the evap with a Russel coil. Added a new TX valve and apropriate supporting components.
I agree, what you wrote about it appears to be a hack job where someone replaced the original unit with the wrong compressor!
I tried to contact the OEM, but alas, they were useless.
I think I remember it was Yuma who gave me some advice on model numbers to use for the retro.