1978 23' potter restoration in progress. Transom questions

[Gulfstreammarine]

Looking for some input: have most restorations been cutting out all the core of the transom and starting from scratch or just leaving that filling in everything and than bolstering up with coosa board to strengthen. I am putting a full Armstrong bracket a 4" atlas jackplate and new Yamaha f300 when done. And of course I am closing the transom in and getting rid of in floor livewell and splashwell and making more deck space. Any input provided I appreciate. Thanks