Hello Colin,
No, sadly, the mod. letters are not elaborated on.
SC and TC models appear to have the same ratios in gearbox.
Any difference must be in final drive between 2000 and 2200 models as top gear ratios are 19.5 mph/1000 rpm for 2000 and 19.7 mph/100 rpm for 2200 models.
Final drive numbers begin 401.... with a T prefix for TC models and 2200 begin 471... total nine digits.
Hope this helps.
Regards, John.