I rashly assume none of these AD heaters are the fresh air design. That being the case I don't see why they would not fit.

I've seen lots of odd heaters installed in old trucks. I pulled a dodge heater out of the '48 I once owned.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...