Ok, first of all, if you have a "classic" stang then you either have a 3 or 4 speed. If its a 3 speed for second gear you should be pushing, not pulling. Anyway, sounds like you do a decent amount of power-shifting so here is an idea. Before some gung-ho guy tells you tear apart your clutch and replace it, try checking the linkage underneath your stick. I had mine slip not too long after I got it and it refused to go into 2nd or 3rd unless I would go from reverse to 2nd or 3rd. It was quite a pain in the neck. Anyway, check that out. If thats the problem just grab a 5/8" wrench and a buddy and have him sit in the car and move it from gear to gear while you are underneath adjusting.
PS - make sure the car isnt running
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1966 Baby blue Coupe, 289, Manual 3-speed, Edelbrock 650, Flowmaster 3-chambers, and minor upgrades. Interior work includes custom paneling, custom dash dress-up(I refuse to cut anything out of the original), Rewiring most of the electronics, Porsche 911 seats installed soon, and Stroker kit when I get to Texas. November of 2001 I will go back to Dallas.