In my humble opinion I would go for the overdrive and look for the hardtop as an add on later. But then of course there is also the 5 speed option to consider if you can't find the overdrive. And there are two conversions for the 5 speed, I personally use the Toyota 5 speed and love that combination. But an overdrive in good working order is possibly better as you get OD in third gear as well as fourth. A friend picked up what I believe to be a factory hardtop just last year. With the freeway speeds we drive at the overdrive is a real pleasure.
You should be able to find a very nice TR6 in very good working order if not mostly restored for above $10,000.
Good luck in your search.
Charley Fitch
