Well, the 1983 204C had a lapstrake hull and the 1985 does not. I'm not sure about 1984, but that should help you date the hull.
They did have transom rot problems, mostly as the result of water leaking through the aluminum trim molding at the top of the splash well.
My 1975 204C needed a transom after 10 years. That was 3 at a wet slip and 7 on a dry stack. The stringers were also developing soft spots when I traded the boat in for another Grady in 1986.
Any 30 year old hull that contains wood will likely need structural work unless it was stored indoors.