Unfortunately, the 70 series would suck all the torque out of my M20B20 and while I could wade across spring time fields it'd be at about 4 kph, with a grinding noise coming from my struts and clutch smoke boiling out the sunroof.
I'm starting to see why the guy I bought the 14" rims from replaced them with 15". They certainly looked good on his Touring, lucky guy.