78 K20 towing with 454 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mattshea125 · 11-23-2019, 12:02 PM

Hello I have a 1978 Chevy K20 that I plan on swapping a big block into with a TH400 transmission. I would like to hear from anyone with some experience on what final drive ratio to go with as I would like it to be able to tow some weight and not be a dog, but have a final drive ratio that isn't screaming too bad a 75 MPH on the highway. The truck has a 2" lift with 265/75R16 tires. I realize that I'm not going to get good gas mileage no matter what, but that's why the truck has 2 fuel tanks right ?

Truck is currently set up with a 350 SB with th350 trans and 4.10 gears and it is really buzzing that 350 at highway speeds.

11-23-2019, 12:02 PM	#1
mattshea125 Registered User Join Date: Jan 2008 Location: Riegelsville P.A Posts: 38	78 K20 towing with 454 Hello I have a 1978 Chevy K20 that I plan on swapping a big block into with a TH400 transmission. I would like to hear from anyone with some experience on what final drive ratio to go with as I would like it to be able to tow some weight and not be a dog, but have a final drive ratio that isn't screaming too bad a 75 MPH on the highway. The truck has a 2" lift with 265/75R16 tires. I realize that I'm not going to get good gas mileage no matter what, but that's why the truck has 2 fuel tanks right ? Truck is currently set up with a 350 SB with th350 trans and 4.10 gears and it is really buzzing that 350 at highway speeds.

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