What size/type of DR on 15" V6 rims

Well, my GF, who's a member here just got some new rims on her ride and i'll be buying 2 of her 15" v6 rims for some Drag Radials. Im pretty sure they are like 15x7's and wanted to know what size drag radial i should run on that size rim (55 or 60 series sidewall? what width will work?). I'll most likely go with the Nittos simply because i've heard they last longer that the BFG DR's.
Also, would you guys recommend that i buy the front 2 as well and stick some small and pretty skinny (165/50/15?) tire on there as well and use them at the track for weight reduction, since my 18" chromies are killing me?

Thanks for your input guys and gals

Well, i was hoping to use the fronts as well to drop alot of weight and changing all 4 at home before going to the track, so i wanted ones that wouldnt wear out too fast since its 60 miles to Houston Raceway Park