Should easily use 8 drams, I would expect. If never expecting to shoot past about 50 or 75 yards, less powder could be used.
I'd likely go a bit slower with the 8 bore - maybe 100", and 80" would work for the smaller sizes.

Greener lists 10 drams for the 8 and 10 bores - that's 273.5gr., by the numbers, and 7 drams (191gr.)for the heaviest of 2 loads for the 12.

Of course, the slower the twist, the more shallow the rifling can be & thus, the looser the fit - perhaps. Much depends on the accuracy needed or demanded.

Those charges are all listed a developing 1,600/1,650fps in 10 and 8 bore and 1,760fps in the 12.

My 12 smoothbore made 1,550fps with 191gr. with a (14bore) 482gr. ball, ball not 1,760fps with a 600gr. ball, and that was from a 24" bls.