Confirmed that OEM the heater core is shot. Leaning towards just getting a brand new, quality core that has the bets chance of lasting a long time. I can get the OEM restored (again) but it is still 50+ year old alloy. I hear the Spectre brand stuff is good.? Anybody use an aftermarket core they can recommend.? Thx

I would get the original rebuilt. I dont think any of the new stuff is up to par as far as quality goes.

With a re-core of your original, all they will keep and re-use is the tanks and they should do an inspection and determine if they are still usable, which they should be.

I have removed the heater core from inside the car, not going to say it’s a 2 minute job but very doable. The lock nuts holding the heater box need to be from inside engine bay and heater control cables removed from heater box.