Your rear will be 8mm taller then the stock 275/40/17 wheels. (0.31").
Which means based on the stock tires your speedometer (if i've done the math right) will read 1.2% lower then it actually is.
So if your speedo is reading 100mph, you are actually doing 101.2mph.
I wouldn't worry about it. (on a side note I believe the 35anniversary cars all came with 285/40/17 and i'm sure they didn't change the program...)