Here's food for thought: Do you drive it enough so that the modification offsets the 'feul' savings? (That was always the counter offensive for gas/deisel boats, driven by large twin engines, and the reason I quit considering the upgrade: deisel is more efficient and gets much better mileage in the water, but the upgrade can cost upward to $50k, just for the powerplantws, not counting whatever modification. It's going to cost you money in fuel anyway, but you can buy a hell of a lot of gas for $50k, making gas engine much cheaper to operate.)

No one has been driving these on the highway for the last 25 or so years. When I made the comment earlier, a nwebie said that he dives his car, but his 1k a year isn't considered driving even by an insurance company. You might get a little out of first gear--I'm not familiar with the finer details--but the od isn't going to save you one red cent in fuel, of offer anyting in the performance department if you drie the car like most owners of these vehicles drive.

If I were to spend the additional amouount that an upgraded tranny costs, I would spend it on additonal hp. Take 2 cars, one with the upgraded tranny and one with additonal ponies and 'twist, the higer hp car will be a much stronger overall performer. And stay with the turbo 350, a well documented high performance tranny.