Copied this off another site, it may help.
I bought my 80 Bu with 12"dual electric fan unit(Flex-a-lite #210) and now that I drive it on hot days it runs warm..I went to Atco last week and it was 85-87 outside and in that heavy traffic on route 73 the engine temp was up at 205 on some on the trip,on the way home it was 70 out and still ran at 180...now going back to my old 87 SS Monte I tried 2 12" fans and found it wanted to go over 210 all the time,till I remove them and installed a 19+" Flex fan (Flex-a-lite#1319) and that droped the temp a lot.............So I bought one for the BU and it was 83 out today so I went out for a test and even in traffic it would not go over 165 and when the traffic started moving it went down to 155.So you want a hell of a good fan try a 1319 Flex-a-lite............... :COOL OLDHEAD,PS: Thats using a stock shroud with the 1319