[Excaliber]

SB Chevs are not known for good mileage, with the exception being late model factory fuel injection on SOME applications. Generally speaking, the 350 is a dog for mileage.

7.5 should be OK for the street, certainly can run that low octane cheap gas! Loose the blower, get a small carb and forget about performance. I would consider a change in cam profile, look for a low rpm "motor home" or "truck" use application for max torque at low rpm.

If you got a solid roller lifter cam your asking for trouble down the road. The kind of cam is NOT recommended for low rpm or "street" use due to oiling of the roller on the lifter issues. 10K "street" miles is about all you can expect if it's a solid roller. Not to mention that cam is probably WHY your getting such bad mileage.