The FLE designation referred to the way the engine was set up. They are all 74 ci and used a low lift cam marked 61 and low compression pistons. Also a small venturi in the carb. It was called a traffic combination and worked very well at low to midrange speeds. Anyone could buy one! I have seen them hooked to sidecars and also for escort use. There was a funeral home in Houston that used to use them for funeral escort. They did not appear until the 61 ceased to be so '53 was the first year offered and '56 the last. By then the FLH was very popular and the cops and commercial customers were buying the regular FL.