I "think" a Gear-Vendor is about $1700. I could be off a little.
Plus figure the labor to shorten the drive shaft.
Go on-line and look at em. Trick stuff . . . Seriously.
Bulletproof too. They were putting them in motorhomes 15 or 20 years ago. They can handle big horsepower motors too.
Not only would it get better mileage but the wear and tear on the eng is cut in half.
1960 Convertible (Orig owner)