Why would you even consider calling here? Even if he is bluffing, you can hardly expect to be winning. You're hoping to call to 4 outs. If you want, we can add the 3 8s, but I doubt it. So, best case, you're a 2:1 dog drawing to a gutshot against a bluff. Against a pair higher than 8s, you're drawing to 4 outs. No real evaluation needed. Even if he shows you a 7 high bluff, you made the right decision.