G70-14 On The Rear?

Need to know if I will have proper clearance to the leaf springs on a stock 1970 Duster 340 (8 3/4" Suregrip) with 14"x 7" Rallye wheels (4 1/4" back space) and GoodYear Polyglas G70-14 bias ply tires. These tires are too expensive to guess wrong, so your help is really appreciated.