I know the part you're referring to. Some 350's had a complicated linkage system at the shift lever, with a really long shift lever that ran on it's own pivot. My wife had a 73 CB350 that was set up like that. We removed that setup and bolted up a 750 shift lever, it was a plug and play mod, so the other way around would work too. I know for a fact that it fits the 750 splines because I've tried it.
mystic_1