i have a mk2 fiesta to give away for free in basingstoke for experiments if anyone is interested? rotten as a pear, so ideal for chopping about

i would like to be able to offer use of the climatic wind tunnel that i work in, but sadly can't

air flow is easy - you just need to open up from an area of high pressure, to an area of low. to find where abouts on the vehicle is high and low pressure areas, you can use a self built manometer

as for fans pushing or pulling - doesn't matter, as long as you have them doing it in the same direction of the natural airflow the ability of the fans to move the air should not particularly differ from pushers to pullers, but check the specs before you buy or just experiment with secondhand ones

alex does have experience of cooling requirements, but don't forget that modern vehicles are designed to be able to cope in 50 deg. C heat situations and you probably won't encounter many of those on uk circuits