RT,
I had a 1988 H33.5. I re bedded all of the stanchions at some point during ownership. The stanchions were thru bolted thru the deck with nuts & washers beneath the deck surface inside the cabin. You will have to pull away some of the overhead lining or carpeting that conceals the nuts inside the cabin. Helps to have someone with a backup wrench when doing this. Not impossible to do alone; however, much easier with a second "wrench". I traced the outline of the stanchion base with a pencil and then taped when re bedding to ease with the cleanup. I used 3M 4200; however, this is another application for butyl tape.