First, you must have an OEM condenser. I'll assume this is the case.
A little (tiny) bit of arcing across the points is normal, but if it's as bad as you say (where you're points are getting trashed), you're condenser is not hooked up properly OR the wires that it is connected to are faulty.
You can't mix and match condensers because if the value is too small, they won't prevent arcing, and if the value is too large, you won't get a spark at the plug.
Consult <a href="http://www.avweb.com/articles/magcheck/">this document</a> under the section titled "The Capacitor" for information about condensers.
Hopefully somebody knows the capacitance of the PC50's condenser.
I guess if you're desperate, you can start with a very high capacitance condenser (too large to let your engine run), and slowly substitute lower and lower capacitance values until your engine will run properly. NOTE: I have never tried this, and I can only hypothesize that this scheme might work. Use this idea only as a last resort.