As someone who has used car fan motors several times these are the stats I generally find they have.

12v
250w
2500 rpm (at 12v)
Weighs 1.6kgs

Run fine at 24v, which quadruples the power output to 1000w (but doubles the rpm obviously).

Of course all motors are different and I can't speak for what Gary has on sale. If you have a manufacturer and model number finding specs online is quite easy.