This thread speaks directly to my desires for the engine I plan to use in my 56 Docge pickup daily driver. I'm mounting the 56 cab/box onto my 2001 2WD Dakota chassis, and ditching the 4.7/5-spd for a built 5.2 Magnum port EFI , as I like the idea of a classic Mopar engine in a vintage pickup. The drivetrain will be the 9.25" 3:55 ratio limited slip rear axle from my Dakota, overdrive trans of about .67 or .62 and stock tire diameter to get on highway revs at about 1800 at 75 mph. I know from many trips driving my 2001 Dakota if I can cruise at 60 mph in 5th gear (.72 ratio) it keeps the RPM just under 2000 and I have recorded fuel mileage over 21mpg. Based on that, with a built 5.2 EFI Magnum producing over 350 ft-lb of torque in the 1600 to 2000 rpm range, I feel its possible to achive consistent 20mpg at 75 mph, and still enjoy over 350 rwhp when I want to stomp on it.

Gene has a 318 in his vintage pickup on a Dakota chassis and said he's gotten 20mpg on occassion. Thanks to Gene's suggestions I ditched the plans for a 4.7HO and will go with the classic build plans for a 5.2 Magnum EFI, Keith Black flat top pistons, deck the block, 5.9 heads, block hugger headers/dual Magnaflo exhaust, Edlebrock Air Gap intake manifold, MSD ignition and whatever else I can plan to create a vintage daily driver that can produce good fuel mileage for highway cruising.