I'm going to be getting a 72 k5 soon. With gas prices and all I'm think of ways to increase MPG. I had a 78 K5 with a HEI, MSD 6A, ALum intake manifold, and installed a 4X4 front wheel locks go to 4X2. I got really good fuel milage aBOUT 12 mpg WITH THAT SET UP. I thinking headers, alum heads, and 5-speed trany with an overdrive gear on the 5th one for high way cruising. My question is what tranny will fit? OR can I go with diffenernt axle gearing to get the job done. It would be gear to get 15MPG. push comes to shove i can always go fuel injected but that sorta pricey.