under which web site would i find real vintage steam train engines for sale.?
i would like to rebuild one or more with an space age liquid nitrogen fuel cell & status of the art technology on board computers and the work’s yet i like the vintage old west style train’s.yet the web sites i pull up are all toy train’s.yahoo’s rep’s could help navigate them.

try ozark mountain rail car
If you can afford to buy a steam locomotive and get it to you, you can hire someone to find you one.
But if anyone has info on buying a real train, TrainWeb will. http://www.trainweb.com/ Try their forums.
You will encounter a great deal of resistance to any idea you may have for converting a steam locomotive to any form of propulsion other than the original steam boiler and engine. Most old locomotives are registered historic sites, and there are preservation authorities that would take you to court. So the first thing you need to do is get a lawyer who specializes in the destruction of historic properties.
Also, very few owners of vintage rail and industrial equipment would be willing to sell an old locomotive to someone who wants to convert it to [I think you mean "liquid hydrogen"] propulsion. It would be a very unpopular idea.
Having said that, two more things:
1. There are at present no “old west style” locomotives for sale. They do come on the market occasionally, to very highly qualified buyers who understand steam locomotives and railroad history. They will not sell to you if they know or suspect your intentions. The last wood-burning 4-4-0 locomotive that changed hands sold for $1,600,000.
2. There are no sales sites for antique rail equipment per se. A good starting place would be to go to http://www.steamlocomotive.com. e-mail the owner of that site; he is as likely as anybody to know what’s on the market just now.
If you don’t have immediate access to millons of US dollars, forget it. There is a heavy 2-8-2 for sale in Canadia for only three million US dollars.
Likely it would be cheaper for you to fake up a engine rather than gut and rebuild a real engine. You also won’t have to fight off railfans that would want to preserve the old engine rather than have a super good idea foisted on a historic machine.