just purchased a 1966 cat 966 b loader sn 57h310 and Im trying to find a sevice manual and a parts book for it cat does not have this one on there computer system yet they started with the 966c, and did this 966b come out with a tubo on it or was that a add on by some one else.This one has just got a straight pipe on it for exhaust and would like to put a muffler on it,if its okay to do it.Thanks