In order to get weight transfer to the rear of your car you will need compliant springs rather than stiff lowering springs, also when you lower a car you lower the center of gravity, which agains hinders weight transfer. Drag springs, from what i hear, are a godsend and help traction dramatically. If you get drag springs, it would be a good idea to get some drag racing shocks/struts to compliment the softer springs.
You can reinforce your torque boxes by having the seams welded so that it's in place stronger and having Southside liftbars with some heavy duty upper control arms should give you great traction. Another thing you can also do is to get a heavier duty rear sway bar or adjustable rear sway bar. I've heard this help even out weight transfer between the rear wheels and provide a straighter launch.
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previous name: 84stangLX
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT