RebekahsZ is right about checking the tires first. I had fitted some 245/45/16 tires to my '76 260z on 16x8 BBS wheels and found that they tram tracked on every uneven section of the road. The tire shape was more of a sharp angle at the edges with a large footprint. On changing to a 225/50/16 profile tire which had more of a rounded edge to the footprint, it was like driving a different car. For a street car the narrower tire worked out better.
For a race car on smooth tracks and without the suspension travel of a street car (which would be on all sorts of rough roads), you can obviously get away with wider tires. As to modifying the cross member or adding Bump steer spacers, well that is up to the individual.
All the best for the New Year.
David (Enzo)