I recently sold a 69 Polara 500 convertible in B7 blue with a black bucket seat interior fully loaded with options including a 440 HP engine to a friend in Arizona. The color combination on that car was fine to me but I would have preferred a white interior instead of black. To each his own.
I usually prefer white interiors if the paint works with it. B7 definitely works with both, but I agree I like white interior best, looks classy to me and really pops.