TRF has an identical one for about $70
Hmm, I see list price under $60, currently on sale for $50. Where are you looking?
I got one from Moss many years ago. Eventually got it to work OK, but the whole experience was very frustrating. At the time, they seemed to have no clue as to which cars had which filter head; or which filter heads their adapter would or would not fit. I was running an earlier engine, with a bypass type filter head on it; and the adapter will not fit the bypass filter heads. They didn't know that, and didn't believe me when I explained it to them. To add insult to injury, the counterman told me "No one has ever complained before", when I knew for a fact that _I_ had complained. They were completely disinterested when I offered to show them both types of filter head and why their adapter did not fit. It was several years before they finally corrected the catalog (and even then the next catalog went back to saying it fit all filter heads).
Installing the full flow filter head from a later engine was certainly no big deal, and probably a good idea to boot. But that experience is just one of the reasons I now prefer to deal with TRF.
As noted, be certain to clean out the groove in the filter head. It's not at all unusual to find the remains of one or even two gaskets hidden in the groove, and they will interfere with mounting the adapter (as well as causing leaks). Also check the adapter carefully for any burrs, nicks or dings in the sealing surfaces.
They are probably different today, but with the one I got you had to be careful how far to screw the threaded piece into the filter head. If I turned it in all the way, there weren't enough threads sticking out for the spin-on can to grab. Took me a couple of tries to get it right.