Yes, you can run the A/C and heat at the same time.
Should be handy on a humid or rainy day when you need to
clear the windshield and take some humnidity out of the
interior. They are switched separately and the
heater/defroster uses the cowl intake door to give you
the choice of either fresh air intake or recirculated
air. All very versatile, but more different switches
and levers in different places than on your modern ride.
Cheers,
Roger
'54, '55, '56, etc.