Like rmesser said -- leak down test.
My first fl350 ran away like that several times and didn't do any damage.
If it does that again all you have to do is floor the throttle and it will shut down if the switch is off.
I know that sounds stupid to floor the throttle on a run away
Engine but it works. It did for me.
You say you never got your jetting right --- I would for sure start with a leak down test and then start over with your carb jets and settings.
Check your intake manifold for a crack and check your fuel pump vacuum line. Do a flow test on your fuel pump for sure - trust me on that one. Your fuel intake lines in the tank might be corroded up as well.
My money right now says you got a big air leak.