John,
Just a suggestion, but before going too much farther you should read through this
detailed oil filter identification tech tip and figure out just which filter unit you have on your '61.
Scroll down to the section covering '60-'63 engines and there is a picture and other details to help identify just which filter unit you have.
Once you do, there are some original GM part numbers noted for the correct filter cartridge you need. Those numbers, plugged in to a basic web search, can provide a list of various brand filters numbers to help you buy the right one.
One note of caution, even though a brand/manufacturer number may show as a good cross-reference to the original number, always check the dimensions on the replacement as some are in fact correct while others have been found to not actually fit.
Let us know how your search turns out or if more info is needed.
Dan
