Hey Uberscott,
You will probably find anything from greenbacks to 65's to 70's to 75's to even 80's/85's or maybe even 100's in it depending upon how it was configured or who owned it. I know that some liked the 80's and ran those. Others liked the sound of the 1982 cabinet that had 100's so swapped for those. Your typical findings will be in the lines of greenbacks, 65's, 70's or 75's. I know that they ran some reissue cabinets at the time also so who knows what is in there. I cannot remember what year that they did it but Marshall was relabeling some of the speakers as their own. These speakers were 70's that were actually 75's but conservatively rated. As far as if they were actually the same G12T-75 as came in the later cabinets I cannot say but I can attest to that as the 75 gets older and more broken in it sounds better than when fresher though still thought of as broken in. The 75 really sounds terrible brand new. The 70s were reissued as classic 70s. To be honest, I cannot recall their having returned to the 65 as standard fare. The 65 is one hella speaker though. The 70 is no slouch either. The 70 is not a V30 though rated for the same wattage. Now the V30 is rated at 65 watts though which I find interesting. Another bit of information on the 75's is that in the newer cabs they don't sound the same either as in the older seasoned cabs. For some reason the older cabs sound better. I am not sure if it is the wood itself or if it is from having resonated so long. It could be the aging of the wood or adhesive between the layers of ply. It could be the adhesive that they used to use. It could even be in the density of the cell structure of the trees at the time the older cabinets were made. It is an unknown but it is sure heard.
Bottomline, if you were happy with the sound coming out, go with it. There is nothing wrong with following your ears. Besides, to each his own. Let the others wonder where you are getting your tone from. Most educated people will know that the majority of the tone you are getting is in your hands and soul and that your gear only helps you to bring it out. The majority of the guitar greats would sound great regardless of what they were playing through. For the rest of us, finding a good starting point for our individual tone is a great foundation for our sound.