first a few questions
*7" wide, what diametre?
*are the wheels fouling the body of the strut or is it the tyres fouling the spring perch?
*what size tyre?

as dattodude said, measure your wheels' backspace (distance from the mounting face to the inner edge of the wheel) for starters...

There are some pretty big variations in the strut body to wheel/hub mounting face in different Datsun/Nissan struts. depending on how much extra clearance you need, you may be able to use another strut (with bigger brakes). I've been meaning to get comparitive measurements of various struts I have in the shed for a while now...I can't give exact measurements at this stage, but MR30 Skyline will give a bit more clearance (maybe 8mm) and R31 Skyline should be even more again (somewhere around 15mm extra I reckon).

But you will probably also have problems at the rear if the wheels are fouling the stanza strut body - the tyre will foul on the inner wheelarch (at least when cornering) unless you are fitting a wider diff.