Planning ahead for my 56 C series pickup build on my 2001 Dakota chassis. My goal is to use a 2008 or newer remanufactured 4.7HO with either a 545RFE or 65RFE trans. The rear axle in my donor Dakota is a 3:55 ratio with drum brakes. I'd like to plan an axle upgrade with disc brakes, but also work the option of rear axle ratio for overall driveability and decent fuel mileage. My reference point:

Back in 2006 my company vehicle was a Ford Explorer 2wd 4.6V8 (300hp) with a six speed trans and 3.55 rear ratio. I did a lot of highway driving, still do, and that Explorer surprised me with better than 22mpg on the highway at 70 mph. At times, loafing along at about 1600 rpm with a tailwind it would exceed 24mpg. So my 56 C series, will be a new 4.7HO V8 and 545RFE, would be over 310hp (headers, dual exhaust, intake, all the usual stuff), similar trans ratios and rear axle ratio, could possibly produce decent highway mileage above 20mpg. My goal is a fun daily driver that gives me grins when I get on it and grins when I rud steady highway speeds. I also want it to be a reasonable driver for my wife, who is not a gear head. So for an axle upgrade to get a strong rear axle with disc brakes, should I consider a slightly lower rear axle ratio to get my highway revs in 5th gear into the 1800 rpm range. I do plan to use the truck as a daily driver, haul my motorcycles, tow my 5x10 tilt bed trailer when needed. Some more perspective too. My current Dakota with the 245hp 4.7 and 5spd manual gives me adequate acceleration. So anything better from that perspective, with 310hp and much more torque (than the old Dakota), in a rear drive pickup would be a fun upgrade to me. If I stay with a 3:55 ratio I'll still get around 2000 rpm on the highway at 70mph. But a slightly lower ratio may still give me decent performance/acceleration and better gas mileage.

I think some Dakotas came with a 3:21 rear axle ratio. But would that be a decent rear axle for over 310hp/350 ft-lb of torque.