Once in a while I get a bug and look at old vehicles that I know I will never buy. That disclaimer out of the way:
From what I can tell, the overdrive option for 3 speed manuals goes back to the 30's, and was somewhat popular in the 50's, and was available through the 60's. Not surprising, even with cheap gas, there have always been those who travel "a lot" per year.
What I don't get is the limitations of them: apparently they could roll away if left in gear, and they were known to freewheel the engine during coasting. I think... I'm not sure why, nor if that was always the case, nor if some judicious mods would fix those problems. I think there was a lever to disable OD and in which case it acted just like a standard 3MT. And I've read that there are some who have disabled the governor and use full manual control so as to split the gears (which is nice as OD was 30% and gearing splits in the trans was more like 60%), but what I don't know if full manual control defeats the freewheeling issue during cruise in 3rd/OD.
[Yes, I know about the 833 4MT with OD that was used in the 70's and going into the 80's. But AFAIK none of them were 3 on a tree cool. 
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[Yes, I know about the 833 4MT with OD that was used in the 70's and going into the 80's. But AFAIK none of them were 3 on a tree cool. ]
