Actually the width of the wheel is important also, as the lager offset moves the wheels inward. Most of the modern wheels are wider than the original 14x6.5 ones, so a 16x7 wheels with a 30mm offset would sit not 5 mm deeper, but 11(+differnce in wheel width/2).

Anybody knows how much room we got to spare between the inner side of the front wheel and the tie-rod?