Mikesbo sends this:
This thing was in excellent condiion. That exhaust had its twin on the other side. Based on that and condition, I'd say this guy is probably making a wee bit more than stock, which means it'll go like stink and then some.
Yamaha moved the engine closer toward the front on the RD400 to try and tame the unintended wheelie proclivity of the RD350. My first bike was the grand-daddy of this one, the YDS3.