I owned a 79/30. Had no problems with the I beam, its normally dry where it is located. BUT---be careful of the chain plates. I had a leak around the hanging closet that rotted a panel where one of the chain plates attached. The fix was not hard, just that it did require a fix.
Also check the engine
. Mine had a raw water
cooled 12HP HORIZONTAL operated piston. That shook the heck out of the boat. I think Hunter changed that engine
in 1980 so you might be OK. I later changed the engine to a 15HP freshwater cooled Universal (Kobuta) which ran flawlessly for years.