I can't help you with the model or schemo, but with regard to the OT and impedance question, the link below discusses this dilemma, how to figure out an unkown transformer. Basically, figure out turns ratio, calculate relfected impedance, make deductions about what your output tubes want to see and what imp. load your speaker(s) will create.
Output Transformer Impedance
also, geofex.com has info on transformer "reverse engineering" and testing.