I can tell you how it is on my '86, yours is probably the same, but no guarantees... Mine has pieces of plywood, maybe 6" x 12" or so, 'glassed into the transom, for three big-ass wood screws for each bracket to screw into. The screws in mine stick out a little bit on the inside. This pic was taken a couple years ago when I had the tank out for other work, but you can see the two top screws of the two starboard brackets sticking out and the rectangle bulges are where the plywood is 'glassed in. Hope this helps, anymore questions, let me know.