Re: I want a 10 second mustang, help!
Work on the suspension. Drag springs, struts and shocks. Drag struts and shocks are a little dangerous on the street, so use adjustable ones and adjust for the track.
In the rear:
Replace the upper and lower control arms with ones that are adjustable, that have rod ends on them. Use a panhard bar to keep the rear from moving side to side. This one is important, reinforce the upper and lower control arm mounting points at the body.
In the front:
get the lead out, reduce the weight. Use a tubular K-member.
Coil-over struts are good for unsprung weight. Strut tower brace.
All the power in the world will get you no where unless you can hook-it. I would start at the rear. Don't forget you safety equipment, drive shaft hoop, roll bar, etc.