Another thing to consider is a "resto-mod" / modern engine. Factory stock exterior and interior appearance, with a modern engine under the hood.
At your current status you don't have to worry that you are "messing up" an all-original / numbers matching car. You now have a "free pass" to do as you please under the hood with a clear conscience :-)
Resto-mod cars do have thier own following, and can bring good prices, so there is still value there. Also, many of the "aging crowd" want to relive thier youth... but without the classic engine maintenance.
Good luck, and keep us posted!