The chassis would have been wider on the plus 8 in those days, having said that its only the length of the horizontal angle iron that varies as far as I can recollect.
I have a towbar on my ‘69 4/4, Factory supplied.


1969 4/4
1995 plus 8
1996 Plus 4 4seater
2002 Aero S1
2013 M3W
2014 Plus 8