I wouldn't use a stock EVO manifold (which would be cast); I'd instead use an aftermarket SS unit like a Gruppe-S or something. That way I get a tested, well-performing, tubular, equal-length unit that keeps the dual scroll T3 outlet.
Figure $400 for the SS manifold, plus another $100 for the proper flange to be CnC'd and welded on. That's not terrible, I don't think... Versus using mild steel weld-L's that I'll pay out the ass for someone to do all the work.
Sounds like a plan to me.