Yeah smaller power return ratio because it makes less power to begin with the increase is going to be so small it might not be noticeable there for you need to package approach it like a full-on everything.
RV cam and a header....but a header and exhaust system at the least before a cam change. Probably go up a jet size or two with the header upgrade.
Ignition,header... then get a 2 barrel intake and a Weber Progressive 2 Barrel on it.
That's the mileage n power increase but with mileage a priority...the a cam or head work.
With every step up in cam size your Shifting the torque higher in the RPM and you're going to have to compensate with a torque converter or some good gears at a certain point and a slant 6 is sensitive because of the lack of v8 umph to begin which makes any low end loss very noticeable.
Really ...it's just another engine
