Phil,
I've moved my focus to new Mahindra and Branson tractors, but in years past Yanmar was our specialty, so my disclaimer is that I am not real current on all of this. I do see some US35's on the web and they look identical to the 990, they even have ROPS, although it looks a little different. I see some AF series, like the AF24 which has power-shift and shuttle-shift. Both models have power-steering of course. The AF is way more advanced than the US35, but not as heavily built. Last I checked I could buy a new Mitsubishi built Mahindra 15 series (dealer cost) for not much more than a used Yanmar AF-series. Cool tractors, but probably best left in Japan.