The 300 truck motor is what I'd use, it's an inch or two taller than the 144/170/200/250 car inline 6. The 300 has 3.98" stroke x 4" bore. Stock, they peak around 280 ft/lbs of torque at 1600 rpm! They're awesome motors. I have one in my old 4x4 full size Bronco, and with a C6 and 3.55 gears, it's getting 19 mpg.