Just did this. ordered the gasket and ring thru J (france), took several months to arrive.
Pulled the whole sprit. installed new ring and gasket. You'll have to shave down the inside of the gasket a bit as it is way too snug out of the box.
easiest to shave the gasket is while its installed, run a blade around starting small and test fitting the pole several times until you've taken off the desired amount (more or less friction).
The Chicago j105 group had a great write up - link below
feel free to reach out direct
Seattle, WA
boat #48