I have an 88 White w/grey interior. Is this color combo rare? All the others I've seen have the burgundy interior.

White with gray is definitely less common, as you noticed. How someone defines "rare" is subjective. I wouldn't call that rare personally, it's in that unique or harder to find category like maroon with gray interiors (85/86 only), both the black/saddle and white/saddle combo's, with white/saddle probably the least common or closest thing to rare. A little more common than your combo but still not as common is black/gray(especially 87/88's) and silver/burgundy, compared to black/burgundy and silver/gray combo's. If you check the SS registry you can get a very rough idea on the color combo's. Small sample size but enough cars in there that I feel it gives a rough % to these types of things.

Thanks for the info.

White and grey complement each other, most cars nowadays have this combination.