Depending on how easy it is, I would look to have the offset changed. On a 3rd gen Nova it seems like a 15x8 wheel wiht 5.5" backspacing will get the most tire within the wheel well (some fine tuning with a spacer seems to depend on the car). The other option is a 15x7 with 4.5", which seems to be much more common. This might give you the option to buy the correct wheel, rather than having them made.
If tall is all you want, then there really shouldn't be an issue. If you want that fat, L60 look, then it may require a little more commitment to the look. Things like relocating the shocks to the other side of the spring.
Here is a decent thread, which I'm sure is popular on all of the Nova sites.
http://www.stevesnovasite.com/forums...ad.php?t=44121
Stolen pic and specs:
Here is 255/70/15 on a 15x7 weld pro star with 4.5" Back spacing
Is Mike gonna be okay with the "de-tune" you'll be puttin on the car with the taller (wimper ratio) and heavier tires?