Hey Unforgiven! I followed your link over.
Whew! Tranny swap stuff nowadays is gonna be tougher than back when we put the 4-speed and Chevelle posi rearend in the '74 Camaro I had. (That was a trip...different types of rearend...pivot already there for the pedal, though...) The Muncie outlasted two rearends, by the way...
We had two auto tranny specialists at the dealership, so I didn't do much more than service them. It would seem to me that finding out if the thing would fit in the car would be the easier part: controlling shifts would be the hard part. On my car the computer decides yes/no on overdrive and convertor lockup both, and they're solenoid activated, if they're like the older ones. I fear that an auto tranny with more speeds would have to use some kind of manual mechanism for the shifting duties, and might not be worth the work. Just personally, I'd rather try to find a stock tranny with taller gears (my car has the taller gears), and go with slimmer but taller tires. A couple of inches of tire size will help a lot, you'll have less mass with fewer gears in the tranny (I'm supposing...) and you can put a gear with one or two less teeth on the vehicle speed sensor to keep speed accurate.
Just my thinking, mind you!
