looks like i caught this one a little late! if you ever need any autocross tips (driving or car setup), let me know. I've run 15-20 events in my 67 Mustang and have countless autocross runs in just about everything else, so I can probably help a bit
glad to hear you had a great time. believe it or not, a classic mustang if setup right and driven well can be VERY competitive. i used to dominate our street tire class until i moved onto driving A&M's Formula SAE car (500 lbs, 75 HP, hehe).
I'm getting back into it again this fall. Probably going to be running Nitto DRs on all 4 corners (like a cheap R compound, but last a little longer) and I'm stiffening the car with a set of Maier racing 700lb springs in the front and matching rear leafs. Should be a good time!