There is a company that supply transformers and parts from China, they can answer a lot of highly technical questions like iron core specification, copper wire resistance and specific calculations, insulation ratings (electrical and thermal) and few other thinks:
http://pa-international.com.au/index.php?option=com_content&view=article&id=122
Come in handy if you have any specific questions and trying to work out parameters of a new transformer been designed.