Im not a car guy, but I know that most of the appeal of those oldtimers lies in their mechanics.
Its like wanting to build a modern quartz movement into an old pocket watch, in the process you rob if of everything that made it special.
It depends on what appeals to you about these older cars. For me it's mostly the looks. I never could stand internal combustion engines between the noise and the stink, so these cars that look nice lost their appeal the minute the key was turned. But stick in a nice, silent electric drive, best of all worlds. Don't like most of what they're making these days, regardless of powertrain. I hate SUVs, pickups, and crossovers with a passion. My own preference has always been very aero, futuristic looking cars. I'm not much of a car guy either. Never owned one, never even had a driver's license. But as an engineer I like to keep up with the state of automotive technology. To me EVs are the most exciting development on the automotive front probably in my lifetime.
My choices:
GT40 with Tesla S chassis
late 90s Mark VIII with Tesla S chassis (I'm partial to this because my brother has one)
1966 Toronado with Tesla S chassis (same reason as above)