There are more things that can go wrong, from broken pump or planetary to small things such as a blown out retention ring in the pump which would bypass all your oil and leave you with no gears.
I'm not 100% sure about this for a 350, but it counts for a 700 trans: There's also a small retention ring on the inner end of the output shaft. Often when you take it off and put it back on it doesn't fit properly, many people don't use a new one... But if that dislodges due to too high pressures your output shaft could slip out of your sungear shell and disconnect everything, especially if your shiftkit is very aggressive it will turn up your pressure so high that you can burst things out...
UC, it could be virtually anything. Your best bet is to pull it apart and have a look, mostly if you have no gears at all left suddenly you'll see what's broken the moment you look into the gadget
Hope I could help,
Max

PS: A torque converter won't brake like that, bets are it's the trans. IF your converter broke to leave you with NO gears, then your vehicle would seriously vibrate even at idle because of bits of turbine flying around inside it(and I mean really seriously).