The gasket (rubber o-ring) that seals the oil filter mount to the engine
on the later B's is probably cooked into a solid mass that appears to be
the bottom of the groove. It probably has a couple of cracks or even a
small section missing. Even if it is not cracked the groove is not deep
enough for 2 gaskets and the new one will probably blow out under 80 lbs
of oil pressure.
When I did mine this past spring I had the cross member out of the car
and I still had a tough time getting at the area. BUT its not impossible.
I used my cordless screwdriver and a 1 1/4 inch long deck screw to chew
away at the hardened gasket without damaging the groove. Once a section
was broken free I was able to get the rest out with my Snap On hook tool.
Make sure that groove is completely clean before reassembling with the
new gasket. Also don't forget to install new copper washers at the line
connections and bolt.
Most of all have fun and keep your sense of humor. I don't envy you for
trying this job with the cross member in the way.