[bobcowan]

This and the other Cobra forum are probably the most active. Between the two boards, there are thousands of people building mostly small block Fords. If you're going to buiuld a Cobra, most people want outragous power. That usually means a stroker.

Fordmuscle is a good one, more technical but not as active.

The Mustang forums are probably not that good for you. Most of the conversations are about asthetics. When they do talk engines, it's usually mod motors.