[Allanw]

If you looking at reducing drag on a Model A, reducing the frontal area is what you want to do! Those posts above, talking about the windscreen etc are spot on.

You not going to be able to reduce the Cd much, but if you can reduce the frontal area, the HP you have will be more effective at moving the vehicle. For economy, you'd have to go slower :-) The increase in HP required to increase speed is very exponential.

A slight tangent: I find it hilarious how car makers spout off about the Cd of the cars they make. The thing is, without knowing the frontal area, the Cd is just a number. You can't use it as an absolute comparison car to car. The only way to compare is to know the frontal area, and the Cd:

Example:
1990 Range Rover Wagon Cd= 0.45 Frontal Area=29.1 sq feet Cdxsq ft=13.1

1990 BMW 325i Convertible Cd= 0.45 Frontal Area=20.9 sq feet Cdxsq ft=9.41

The BMW is still a LOT easier to push through the air!