First Auto X in the valiant.

Don't mean to highjack your thread. I'm building a 65 Dart PT/ Autocross car. So any info I can gather is great. First hand knowledge from anyone is always welcome. Rear Tires size is no problem as I am doing a mini tub. But the fronts on my car is a big problem. I would love to run a 17x8 or 9 up front. just don't think I can fit a 9 under it.
Heres a question that one of you guys might be able to answer that I'm having no luck finding.
When lowering the car with the T/bar should you use a stiffer T/bar to make up for unloading the T/bar? I'm guessing that the T/bar system uses a preload to determine sprimg weight to original ride height?