What back space for 15 x 10 cragar S/S wheels on 67 dart

I started with 295 tires but they were hard to come by so I stepped up to 325 nitto drag radial.
I also use a stock a body 8 3/4 and home made steel rims with dog dish caps. 15 x 10 rims with 7 1/4 backspace (big bolt pattern 28 inch axles)