Hey there Kruser,
Those are some sick wheels you've picked out!
Ummm, original tires for that would have been an E78-14 I think, which translates roughly to a 195/75/14 or a 205/70/14.
Are you wanting to run the same size tires front and back?
If so, I believe that you could safely get away with 225/60/15 which would fit both the 15x7 and the 15x8.
The 215/65/15's Bog mentioned would work too, however, I believe that the over all Rim Width Range for those tires is only 6 - 7.5 which could possibly pose a problem for the 15x8, tho I do not know for sure.
Hope this helps.