I guess in 81 they were still figuring out the methods of construction as the flooring in mine is 3/4.
My plan is to use polyester resin due to cost. I did find HDPE structural lumber, but that would require even more expensive epoxy. I have not thrown out laminating 3/4" Coosa as a single 4x8 sheet should make one of the main stringers. So I would be looking at 3 4x8x3/4 sheets (stringers) and 1 4x8x1/2 (transom).
Michael, I may hit you up if I can't get the original pylon out per Mischief's suggestion.