Tha digital signals are being broadcast by most stations, especially in larger cities.
We installed a 20" Vizio HD in our 1965 Caravel
a year ago. The only problem is, I should have put in a bigger set. The old antenna, the folding one outside on the left front corner, with the little handle inside to turn it, works just fine. If your antenna has a UHF loop built in, which most all have since the 60s, it will pick up digital broadcast just fine.
As far as a box to convert your old TV to play digital, that's up to you.....But...after seeing HD on a new, flat, bright screen, I don't have an old "tube" TV I want to spend the converter money to watch.
Does the saying "throwing good money after bad" ring a bell?