Oddly enough, the mk1 "Sport" never came out of the factory as a "Sport". It was actually something that was done to a standard Mk1 when it hit British shores. The dealers put the lowered springs on, the wheels, the grill and the decals. They were given the 8½" all round (I think they are 8½), with the option of the the 10" rears, but technically, nothing on it was a factory option.
Rubber aint cheap, last Continental Sport Contact 2's that I bought were £187 each, last pair of Eagle F1 GSD3's were £300 for the pair. Bagged a pair of Ultracs off Gord for £150 (bargain :) ). Last pair of Falken FK452's were £280 if I remember correctly.