Suggestion on New 3rd Member

Street Strip. 68 Barracuda notchback, right around 3100 lbs. I presume. I went ahead and ordered a 3rd member w/powertraxx and 4.11's. Going from 26 inch diameter BFG's w/3.91's to 28 inch diameter M/T's w/4.11. Hope I don't lose too much gear. However right now it does nothing but spin the little BFG's and desperately need traction. I don't drive on the freeway as I live in a rural area. Just around town. Will trailer to 1/8th mile and 1/4 mile track.