Difference in chassis and body R50/53 → R56, Cooper → Cooper S
I am new to Minis and have a basic but maybe a little intricate question. I would like to know what the main differences in chassis and body are, first between R50/53 Cooper and R50/53 Cooper S and then same for the R50/53 Cooper S and the R56 Cooper S. In all cases, if it matters, it is the convertibles of each model I am interested in.
The reason I ask is that I am, before buying a Cooper S (or maybe a JCW) R56 am looking into what it would take to have a R56 approved or authorized for a tow bar (except moving the exhaust pipe).
I would expect an answer like "better brakes, stiffer suspension and stronger frame". I don't need all gritty details but only the main differences (but it would be good with a brief specification of how the brakes are better etc).