In your first post, the 1st pic is a Series 2 and the 2nd pic is a Series 1.  The major differences between the Series 1 and 2 is the styling and cab.  Series 1 had 48" cab like you described and the Series 2s were 60" wide with a full width dash, tilt steering, small buddy seat, more like a Steiger cab.  I have a 1978 Series 2 HN 320 which has a cab just like the 1st one in the pic and it isn't any louder then the cab on our 1982 Steiger.  You can tell the year of a Big Bud looking at the serial number.  The first two numbers are the year.  For example on mine it is 7838 which means 1978, 38th tractor built that year.