I've installed a few of them for customers. They work decent considering everything is small. I've heard a few complaints from others that they don't blow quite cold enough but it can be 115-120 in Phoenix though so take those complaints with a grain of salt (even factory AC units struggle with those temps, especially in a dark color car). Plus considering the condenser is small, the evap is small, the compressors are small, it's a very compact package that doesn't hold a lot of freon, so you can't expect frigid temps. They don't work as well as a factory engineered setup, but they do an okay job keeping you more comfortable.
Last one I did was on a 57 T-bird. It would only hold 12 ounces of Freon (1.5 cans) and the pressures were spot on if that gives you an idea on how small the package is. We put an electric fan on it as well to help pull more air across the condenser which helps to keep pressure down and cool the charge. Being a 2 seater with very small passenger compartment it actually does a decent job.
Texas being more humid than AZ, the vintage AC would probably feel pretty good if it just pulled the moisture out of the air, that alone would make you feel more comfortable and be a huge improvement.
