312 Oil filter adapter plate
 

Last oil change oil filter adapter plate loosened when spin on oil filter was removed. Tightend back up but should something like lock tight be put on the bolt that connects to block to help hold it from loosening during filter change?

The instructions with the adaptor I bought suggested that lock tight be used, and how tight are you turning the filter?

The torque spec for that "bolt" is 20-25 ftlbs according to my '61 shop manual. That is far more than should be required to loosen the filter and it should not come loose when torqued correctly.
I don't recall the size of the nut but what you want to do with the socket you use is to use a belt sander to grind the inside chamfer off so that the socket engages more of the thin hex of the bolt, to avoid slipping off and rounding it.

Oil filter adapter plate
 

Next go around I will check the torque on that bolt. Thanks