OK, despite my concerns over strength of new bolts, I needed the space and decided to mount the bracket.
As this will be a refurbishment, not a restore, and I'll be using it as i fix it up, I know I won't get to the exterior for 2-3 years. So I decided to experiment a bit. The exterior of bracket is painted with rustoleum marine paint, the interior with rustoleum professional. If one or both hod up, greatt! If not, easy to clean and do over.
I replaced the Original solid teak wood mount with a marine plywood one, and the other galvanized bolts with stainles grade 5, along with some additional heavy duty washers just for overkill. I used a LOT of marine sealant on it as it appears that the bottom of the bracket sits in the water when it is launched.
Interestingly, the inside where the large bolts go trough has these angled washers so the bolts sit square (the actual transom is curved). They ere handy.
So, with o further ado, hee are the pics: