I think I finally figured it out from an example in
this paper. The target parameters are in pounds, pounds per mph, and pounds per mph squared. So F=A+Bv+Cv^2, where F is in pounds-force and v is in mph.
So power at a particular speed would be P = (Av + Bv^2 + Cv^3)/375, where P is horsepower and v is mph. This seems reasonable... about 40 hp at 60mph for the worst SUV's, about 15 for the best cars.