well, I have been down this exact road. Matter of fact, I'm still travelling it. Do not attempt to hang a bracket on the back until after you cut it open. Mine had a 12 x 18 inch piece of 1/2" ply for a transom that was barely glassed to the hull. Bolting a bracket to it would have surely ripped it apart. I made a new complete transom that fits the entire back of the hull from two layers of 3/4 marine ply and glassed it in with west systems epoxy. I added two knees from the transom to the tunnel to stop the flex as well. I added two full length composite and glassed in stringers because they bend in the middle. I glassed in the bucket as well because the only thing holding in the liner was the rub rail screws and some crappy (off the shop floor) garbage and resin mixed into filler. I cut out 50 lbs of water logged green foam near the bilge pumps and then foam filled the entire hull under the liner to stop the floor from flexing. I epoxy filled the drain holes in the liner too. The idea being that I would rather bail a little water oft of the cockpit liner than have it in the bilge all the time. They are a very wet ride but its nice on a hot sunny day.
I fabbed up a 6 inch set bak and manual bracket for the 40 short shaft thats goin on it next summer as well.
Next is cut all the old wood out of the deck, repair the cracks and strengthen the fore deck where the gas filler neck comes thru.
My tank is an 8 gallon aluminum made to fit across the tunnel hump in the liner below the dash.
When the deck is done it will be bonded on and glassed all the way around before prep and paint. I figure that when ir rolls, I want to be able to slavage the boat so strong is good