I've recently had an old Fender Bassman Tube head refurbished, and I'm trying to find a good match for a cabinet. Is there a good method for sizing a cab? Also, in trying to figure out what year the head is, the only serial number I've found is AB 165. Is anyone familiar with how to interpret this? Or is there another number hidden away somewhere? I tried searching this subject but didn't really find any good info. Thanks!