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burnin oil · 09-28-2021, 08:34 AM

I dont think that gear swap is going to help you unfortunately. I just hauled gravel with my 57 GMC D250 and with 3 tons on the back it was right at 12k pounds. It was all it could do to pull a grade, even configured with 5.14s, granny 4spd, and a SBC. My milage was around 5 or 6. The motor is a stock 305HO. Not the best but not shabby for a stocker. Truck is spinning about 3k rpm at 55mph.

My thought for the wieght is deep gears, 454, and an OD trans. A cummins diesel would actually fit the bill better but you didn't ask and it would be a ton of work. I towed a 12k camper with a 5spd and 3.55 gears comfortably.

09-28-2021, 08:34 AM	#21
burnin oil Registered User Join Date: Jan 2013 Location: Eastern TN Posts: 1,921	Re: 1970 L47 400 BB Torque and HP chart I dont think that gear swap is going to help you unfortunately. I just hauled gravel with my 57 GMC D250 and with 3 tons on the back it was right at 12k pounds. It was all it could do to pull a grade, even configured with 5.14s, granny 4spd, and a SBC. My milage was around 5 or 6. The motor is a stock 305HO. Not the best but not shabby for a stocker. Truck is spinning about 3k rpm at 55mph. My thought for the wieght is deep gears, 454, and an OD trans. A cummins diesel would actually fit the bill better but you didn't ask and it would be a ton of work. I towed a 12k camper with a 5spd and 3.55 gears comfortably.