I/O to bracket conversion question.

[Bikecop1]

Got a question on adding a transom bracket. I’m looking at a 20 Seafari with an inboard outboard motor. Early 70’s model. The motor is a Chrysler 4 cylinder. Don’t know anything about them or if parts are even available. If I were to pull the motor and add a bracket, would I have to redo the entire transom or would having the hole sealed suffice for the bracket. Thanks for your help.