Intersting. The shop manual only lists the 1 quart filter for the 261. I also have a 261 oil filter on my 235 that came from a '60, it only holds 1 quart as well. Looks like there's an option, you're going to need to verify which filter you have.
BTW, yes, I'm still kicking myself for not getting the rest of that 261. Meant to go back and get it, but the yard finally cleared out all the vintage stuff earlier this year.
