dirtyfunkg: If you can send me pics of the cones, front and back, I can usually tell if it's a recone, or if I reconed it. Looks like you've got the standard series/parallel wiring, so the cab should be 16 ohms. That center post is definitely not older than 74/75, as it's too small to be the 73 and older large center post. If these are all 25w G12M 16 ohm (T1221), then your 2203 is going to kill them. It's 115w clean and over 170w when cranked past 7 on the volume knob. Here's a JCM800 spec sheet I made into a jpeg.
http://scumbackspeakers.com/specs/jcm800powerspecs.jpg
Shoot me an email with more info & pics and I'll try to help you out.