I changed my '57 Belair wagon to DOT5 in the mid 80s. I rebuilt the wheel cyclinders with the standard kit from the parts store. I didn't rebuild the master cyclinder. I have driven it for 20 years with no problems. Maybe I got lucky.
I do have a problem with my '56 with DOT3. After not driving it for a year the brakes grab really bad. I haven't checked it out but I'm guessing it is rusted up wheel cyclinders.
Maybe one reason Wagner doesn't reccomend DOT5 is because they don't make it. Ford Motor Co. doesn't reccomend driving Chevys either.
