To be honest this is very very difficult.
Unless this confirms from source charting, things are going to be difficult.
Talking about PT, they would first be used to clear GNWL and CKWL from source post which they either might be released for current booking or left unused for the TTE. Another alternate is to transfer those vacant berths to the next charting station which is in this case is BZA. Now either of these (the last two) might happen or might not happen.
SC...
more... is not very far away from BZA, so you really do not have to shed much if you book from SC keeping boarding point as BZA.
Right now, 2AC has status GNWL 1 and CKWL 1 while 3AC has GNWL 3 and CKWL 1 while PT for 2AC is 5 and for 3AC is 17.
So, both 2AC and 3AC GNWL will confirm easily.
I would recommend not to take chances with this and go for booking ex-SC with boarding point as BZA.
Good Luck.