I'm planning a trip to Utah. I have $150 to get there. It's approximately 668 miles. I'll be pulling a ~20' enclosed trailer full of household stuff (friends moving).

The truck is a 74 w200 with a 1972 440. I have a street avenger (670) carb and K&N filter. Truck runs awesome. I just did head gaskets. All upper seals redone. New radiator, hoses, front brakes, power steering pump and hoses, new belts, etc.

My speedometer is broken and my fuel gauge is unknown accuracy.

Should I calculate 10mpgs to be safe?