Hi All,
The Columbia 'Coffin' type ring on the bike looks to be from a Columbia G519, so is the correct size, just replaced at some stage, possibly during its military service. Personally I would leave it be until an original Huffman one came along. The crank and pedals are incorrect, but suitable ones are not too hard to find.
The 'correct' fork would be difficult to find, it is the early Huffman G519 type, so the supports for the rods are welded to it, rather than as a separate bracket on later Huffmans, and all Columbia's. Again, if it were me, I'd probably find and fit a later fork and bracket (not too hard) then keep watch for the correct fork.
There are a lot of parts missing to convert it back to a G519, but most of the really difficult parts (other than the fork, which is a real pity) are still there.
Best Regards,
Adrian