This horn has little market value and would accumulate more value being cut if it were a good F.
Then you could be the lead designer in the new Conn F tuba!

It does look to be pretty easy as a good bit of the upfront tubing is fairly cylindrical.
I am assuming you would build your own valveset for the horn, as under .700 bore four-valve sets are fairly tough to find. From looking at the horn's branches, bows, and bell, I would be pron to think it would have a bit more projection than the YFB-822.
Go ahead and take the chance, Joe!