I don't believe that the 15 x 8.5 with the 3.75 back space will fit very nicely under your chevelle. I used to run 15 x 8 cragar mags and also weld wheels 15 x 8 with the same backspacing as yours with 275/60-15 tires in the rear. Fit was great. I had the 15 x 8.5 torque thrust D wheels on my 62 Belair, I know that they would not fit under the Chevelle.
they didn'y fit that nicely under the Belair either. too much wheel on the outside towards the quarter panel lip.
they didn'y fit that nicely under the Belair either. too much wheel on the outside towards the quarter panel lip.