Thank you Dan and Bob for sharing your info on this topic!
I have several period aftermarket filters made by Bowes, Fram, AC, and Wix. Some are maroon and some orange, the Wix is a little weird in one side is maroon, the other sid black. IIRC the application on the box is early Avanti but otherwise the dimensions are identical to the HiPo.
The Fram and AC are a little smaller diameter and do not fill out the air cleaner as well as the others. I assume those are a little later vintage?