Try the Tuning Factory in Farmington. My old tech/fabricator works over there now and can definatly build you a nice stainless equal length manifold as well as all the other piping. His name is Kenny.
Another place you might try is Gilsbach Race craft. Bill is a friend of mine from way back and is probably the best race fabricator in the midwest.
http://www.gilsbachracecraft.com
Bill would be my first choice if he has time to do it...He built the Turbo system on my WS6 and its probably the sickest system ive ever seen...pics are on his site
...call Kenny over at the tuning factory thought and tell him I reccommended him. I will vouch for his work as I have watched him build stainless manifolds over night that were just sick. When he worked at my shop back in detroit we banged out the worlds first turbo H3 Hummer and we only had the truck over night...it showed at Sema. He knows his ****...it will be pricy if you want it nice and out of quality materials...just a heads up.
hopefully this helps...goodluck with your project.
-Scott