My friends have 69 Camaros w/ 17 x 8 on 245/40's front and 17 x 9.5 on 275/40's rear.
Their drops were similar to what you're planning. As long as the overall tire height is about the same I don't see why you can't run the same widths using different wheel diameters. If you decide on taller tires, that would be a different ballgame.
You might want to check this site for other opinions
http://www.camaros.net/