So I want to get one of those tachs that have the trip computer in them. that can show you speed and other things. My question is how can I tell the difference between those and the regular ones that just tell temperature?

 

No difference.
Youe need to retrofit the On Board Computer (OBC).
see here :-

www.outmotoring.com/images/how_to/MIN_OBC_gen1.PDF

 

The instructions say R50. Can this not be done on an R53? Which years?

 

thats awesome thanks. I cant believe it such a complicated process. I thought you could just plug and bolt the other one on. Does mini sell this retrofit kit?