The scientists used SI units but the vehicles were made by traditional US aero shops, using imperial units.new guy smart comment - but it was good enough to put man on the moon and bring him back again!
kinetic energy is measured in joules. lb-ft is a measure or torque, not energy.So first i'm gonna convert some units; 1400 kg is about 3100 lbs, divide this Weight by gravity, g, to get mass, m; and 70 mph is a velocity, v, of about 103 ft/sec.
Now the kinetic energy of motion at 70 mph is (.5mv^2) = 510682 lb-ft
For a first order power estimate take the kinetic energy divided by your acceleration time, let's assume 0 to 70 in 13 seconds.
This gives a power of 39283 lb-ft/sec, a horse can pull 550 pounds over a distance of one foot in one second, so divide by 55