Sounds like 50 is about average advance with engine up to speed and everything hooked up. I ended up cutting mine back down to about 44. 50 just seemed like too much.
Got something weird going on now. Since i changed to mani vac now the car idles pretty good but sometimes the engine will just start losing rpms and eventually just die altogether. Almost like its running out of gas. Maybe just need to add more fuel to the idle circuit. Carb tune on the to do list.