I am having the same issues with a 57 235 in my 37 p/u,I have a 54 water pump on the adapter and only have 1/4 between the fan and radiator and I would be screwed if I had to change the belt on the road. I have been doing some research on different fans I seen on ebay and this forum and have found what looks to be a original 37 truck fan that should give me a extra 1/2 inch from what I have with the present fan,it presently has a 49 to 54 car fan which looks to stick out further then a original. I have found that the fans various vendors sell is the 49 to 54 car style which was probably the replacement from the dealer way back when since its the last design fan for those motors,if you do not have the original 37 fan I think the fans up to one from a 41 car might leave a little more space. I am going to go to a local old junkyard if its nice this weekend to see what I can find if the fan I have coming does not work.