The problem with older low angle planes is the strength (or lack of strength) of the material in the body (iron or wood). Older cast iron low angle planes often developed cracks in the body at the back corners of the mouth (on the sides of what would be the frog on higher angle planes). Newer low angle planes use better metal for the body and they're less prone to those cracks.
If you want to go low angle, you're better off with a new low angle plane. The older ones are sought after by collectors so they're priced about the same as a new low angle plane. This is one place that older is definitely not better.
Mike