My 74 Duster with a 225 Slant has a two barrel intake and two barrel Holley off of a 318. It runs smooth. It usually gets 15-17 mpg on the hwy and 11-13 in the city. It has some miles on it and the valve seals may be needing to be replaced, but it runs smooth on all 6. The gearing is 2.76 behind a 904. Does this milage sound reasonable for a setup like this, or should it be a tad better? The valve lash seems alright, as there is no valvetrain noise. The exhaust manifold leaks a bit, as the idiot who had it prior to me did not put much of a gasket on, mostly RTV( ). I am going to fix that this weekend.