Well here is a picture of the two common factory heaters.
http://www.flickr.com/photos/advance-design_parts_co/8129448404/in/set-72157631868452754
A couple questions are you looking to remain old school correct? There are numerous street rod alternatives if you are not that others may have direct knowledge of. If you are looking at the original types then probably the best is the 1953-1st series 55 type with the door. I have lots of heater pictures for you to look through.
http://www.flickr.com/photos/advance-design_parts_co/8129313579/in/set-72157631868452754
With the small cab a good rebuilt heater should work great, I have not heard of the recirculating heater issue as you have stated. I do not use my truck with a recirculating heater in the cold but others probably do and they will chime in as to effectiveness.
The recirculating heater has a round core which is difficult to source, the Air-Flow core is now available in reproduction.

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr