it also depends whether its a 2 or 3 bolt front end
the 2 bolt front ends have about 15mm per side wider front track
ive got 17x7 all round on my bug which has 3 bolt topline front end and et40 rims are a perfect fit
ive got rear discs on the back which add about 10mm per side but even before these were on it didnt look any different
but if u had a 2 bolt front end u would need et50-55 on the front