Addition of O.D's, fuel injection, and rear wheel disc brakes, usually offer no real advantage let alone never pay for themselves.

Especially in hobby cars. It's more for bragging rights.

I enjoyed my cars when they were current, and more so now that they are rare and different.

I believe properly maintained drum brakes work just fine for someone that drives reasonably safe in the first place. They only fade after repeated hammering. Not really needed. Even on today's freeways. Most folks just drive way to aggressively today. Not to mention all the other things folks do while driving on those commutes.
My reason for swapping would simply be availability issues.

The above mention of crashed newer cars bares out this belief.
It's not the car so much as the nut that holds the wheel.