Looking for overdrive trani advice for /6, please help

You NEED a turbo. The turbo will increase MPG more than the OD.

Sorry, I couldn't help that. I personally like the idea of the 200R4, had one in my old El Camino. Easy to find, and cheap, although I don't know squat about the conversion process.

Seriously, though, a properly done turbo can increase your MPG, but I'm not recommending it (or against). Just being a wiseguy.