If none of the presets have the exact sound you need, you can modify the Manual and Resonance parameters of the one that is the closest to your desired sound.
MPescuma as others have already mentioned, the first step is to make sure you have downloaded the Wah presets from the link earlier in this thread. This includes settings for nearly every major wah ever made. If it isn't in the list and you have the original, or know someone who does you can make a sound file of it and send it to Don who will try to recreate the sound and add it to the preset list.
Thanks ! I did not download the patches yet, will give it a try today. Thank you for the tips on tweeking the settings as well.