Mine is a 4' side shift with a gear final drive. Made in Italy.
The chain drive is in an oil bath, which is, as I understand the way chains are supposed to be. A chain in an oil bath last a long time while one 'out in the open' like my haybine, and baler wear out quickly. Lots of vehicles use chain for timing and last as long as the engine does.
In terms of advice, I'd suggest not going too big. With a side shift tiller you adjust it so it tills behind the right wheel.The thing with a PTO tiller is, it does a lot of work real fast so, unless you are doing this for a living there isn't much benefit from going big. Every spring I till my garden (about 1/2 acre) and a few of the neighbour's as well in less than a couple hours. Of course, if you have nice soft soil, big isn't bad, but we have rocky stuff that gets real hard.
Oh yeah - make sure you get one with a slip clutch PTO, otherwise, any rocks and you'll shear a pin.