Yes, taking the bolt out will allow the canister to come off. You might have to jostle it a bit for it come off. don't forget to remove the gasket. Powdercating shouldn't hurt a thing.
On a side note, you'll want to confirm which canister you have, as there was both a 1 quart and a 2 quart version. Seems that there is a discrepancy on 261 oil capacity, the owners manual says 2 quarts, as Tim has posted. But the shop manual says 1 quart. I have seen hoth styles on 261s, and have a 1 quart filter (PH141 element) from a '61 2 ton on my own truck.
