I would contact Kerry Thalman through his web site. Nick has provided the link. He will certainly have some information if there is any out there. It may not be on his list beacuse he hasn't gotten one to look over. If anyone can help you, Kerry can. I met him at this year's LF meeting and he is a very decent man who is willing to share information.
I don't know of a 300 SW, but my 300mm Symmar-S f5.6 is a beast of a lens for 8x10. You may be looking at a rather large chunk of change if you find one to use. Please let us know what you find, as it is interesting. tim