Sheared Keel Bolt Repair

My aft keelbolts sheared off just at the level of the bilge floor. The plan is to chip away the resin around the bolt to a sufficient depth to accept a coupling nut:


Then a new threaded rod would be screwed on from the top, and the whole thing refilled with resin.

Questions:
1. What is the size and thread-count of the existing bolts? My boat is a '95 TPI. I'm away from the boat, otherwise I would measure it myself.
2. Does anyone have a...

Sheared Keel Bolt Repair