Dimensions of my 2 Dart pulleys. Approx 5 3/4" top, 6 1/2" bottom. 5 1/2" top, 7" bottom. Neither have a cooling problem. My '69 is a 418 stroker, Flowkooler water pump and Cold Case radiator. My stock 318 a/c car has a stock water pump and stock Glen Ray radiator. Both have the 2863 216/215 fan and Hayden #2947 clutch.