My VolvOldsmobile ('76 265 body, '63 Olds 215) got 21 mpg on it's last trip with a recently freshened motor, before the 250k Roto-Hydramatic gave up. That was with direct top gear and 3:31 in the rear. The motor is the basic low compression, 2bbl version with a mild, torquey Crower cam. It's been in storage a long time now but I'm ready to redo it with a '93 245 body and Camaro T5. I think Rover made 4.6 and 4.9 versions--shouldn't be hard to pull 300hp from that displacement and they weigh no more than the red block 4--makes handling, braking, springing and shock choice non-issues. Rover used a version of the HP22 auto transmission (so there's a bell housing available) and BMW also used that transmssion in some 6 cyl models (so there are rear drive versions beefier than those found in Volvos). I was first thinking along those lines to keep mine an automatic but feel that as long as my left leg is still working I'd rather it was a stick. Between the switch to stick and having an o'drive top gear I'm looking for mileage in the high 20's -- and it's a kick for my head knowing I've got the basics of a 2 time Formula 1 championship winning motor.