The 350F had its own breakerplate and points when it first came out: Honda stated thru their service reps that this was "due to the higher redline RPM of the engines". IIRC the 350F/400f versions (-333- numbers) had thicker springs on them, maybe check yours to see if that's true?
The first 350F backplates for the points did not fit on (my) 750K2 when I tried it: the slots on the lower part of the plate looked much like the slots on TEC's current backplate, with the lower slots narrower (but clocked slightly off to one direction) in width than the upper one by just enough to not let the 2-3 side point reach their timing marks (too far advanced at 0.012" minimum gap). The ones on the old 350F were like that, and on my oldest 750 versions the slots are the same widths: this changed in the 1990s 'unification' changes by Honda when lots of these parts numbers got mish-mashed together into something 'universal' instead. They were just trying to reduce part number counts so they could supply parts that would run still, because of people like us who won't quit riding their bikes...I wish Honda had also widened the lower 2 slots of the [current] TEC plates when they did this, so they would fit ALL the SOHC4 bikes like a universal part.
I've not heard of any 'points bounce' problems from weak springs when using 750 points on a 350F/400F, though.
While I am not sure [at the moment]
WHERE I have them, I have an old -333- plate and one of my earliest -300- plates (I think it is Hitachi), so if I can remember how to look for them I'll try to dig them out. I kept them just for this reason, as I [more than once] tried to tune up 350F bikes with the 'other' points plates, not getting stellar results. That's why I saved these, to try to make me remember this.