I have a 77 MGB that I use as semi daily driver. Wish it had OD but it’s fun to drive. My son is trying to talk me into dropping a 6 banger in it, but I may look for another to modify.
There is an aftermarket overdrive for vintage CJ jeeps like my 65.
Not cheap and I can’t see doing it. However, there would be 5 levers. That would confuse a modern person who has no concept of the manual transmission.