Best way to get better gas mileage out of my 454 1961 K20

[61Chevy454]

Hey guys, here's the good news...I'm almost into a job that will have me making $50,000 a year for the first 2 years, and $70,000 a year after that.

The bad news? My truck gets 9.92 MPG at its best and god knows how bad at it's worst, and the job is 70+ miles each way.

What I was thinking of doing was buying a rebuilt small block 350, throwing a Holley/MSD/FastEFI/Edelbrock EFI system on it. That plus my 700R4 Should net me reasonable MPG PLUS increase the value of my truck PLUS be more reliable because of the rebuilt transmission and rebuilt crate motor, and it's A LOT cheaper than my other option which is buying a new car.

What are your opinions? What kind of motor should I go with? Any good companies that don't charge an arm and a leg?

Thanks,

Ben

P.S Anyone have any ideas for best way to install seatbelts in the 61 model year trucks?