1974 200 l6 3 on the tree 4.56 gears on p235 all tarain pizza cutters a solid 21 mpg at 3500 rpm top speed of 58 mph all day long. Now on the other 76 stock 302 m5od 350 gears and 33x12.50 I get roughly 12-14 mpg at just about any speed under 70 mph anything over that and it goes down bad.