We build our plow motors just to get good mileage.All are 350's,9.0:1,stock 194 heads with exhaust port work,SMALL cams (.390 lift/194 dur) advanced 6 deg,stock exh manifolds,2 inch duals,performer intakes,modded holley 600's (vac sec) and a reworked dist.
Running 235/85R16's and 3.42 gears with turbo 350,most get 18-20 MPG on the highway,and will use a up approx 20 Gals for 12 Hrs of non-stop hard plowing.
With even a stock 350,we were getting 14-16 MPG and 20 Gals would barely go 6-7 Hrs
I still find it hard to believe you go 30+ hrs on $35.00,especially with eveything in that motor