I dropped in on Valenti Tractor and Equipment in Troy, NH on Saturday.
He is "back in again" as a Branson dealer, after a few years of (almost) retirement.
We had a long chat, during which he confirmed that the R series is little more than a "cosmetic model year upgrade", i.e. same tractor with a little more power and pollution compliance (Tier n).
With turbos they have upped the power, top o' the line is 55 HP.
It seems kinda odd that they don't lower the compression on the turbo models, I'm a bit suspicious of that, but admit to not being current on small diesel engine design.
I would be watching exhaust temperature on one of these.
For anyone in the area Valenti is right there on Rte 12, just a little bit north of the black and yellow dealership (-: