Unless you're getting a bike for racing, you can probably fit a range of bikes. According to some formulas I've seen, I should be riding anywhere from 51.5 cm to 53.5 cm - but I have no problems on anything up to about 57 cm (c-c even). I'm 5'9" and of relatively ordinary proportions. If I got one of those 52 cm bikes, my saddle would be way on top of a pole, and I'd need a stem that would be absurdly long.

I think that 55-56 cm is a good average starting point for someone 5'10". Getting sized by the lbs can help, but with a vintage bike, you probably won't be getting compact geometry.