Same is true of used cars, aircraft, boats and any number of regulated products. Change any tiny reg and all the previous stock "could not be built today". It doesn't mean much. Buildings last decades, centuries, far longer than any zoning board decision.
Aircraft are a different case than the others above. Aircraft are built to a type certificate and once it's issued so long as that type certificate is not revoked, airplanes can (in fact, must) be built today in conformance with that type certificate. Modifications to that type certificate are permitted, but they do not require full conformance with current regulations.
My 1997 airplane was built on a type certificate first issued in 1956 (under CAR-3 regulations) and amended to include my model in 1969. Many regulations changed between 1969 and 1997. Beechcraft could build one today under that type certificate, even though they couldn't get that exact type certificate newly issued today (CAR-3 has been replaced by Part 23 requirements).
Yes but the new aircraft would have to have things like modern electronics, not the pure original spec. The wings could be unchanged but the radio set would be to current standards, incorporating things like adsb transponders that didn't exist in the 50s.
The only avionics change since 1930s that would be required is radio with modern channel spacing, unless you want to fly in controlled airspace, then a transponder would be added (which would incorporate ads-b functionality, whether by integrated or add-on GPS)
