http://cgi.ebay.com/A-MAZDA-RX7-13B-...713.m153.l1262
http://cgi.ebay.com/MAZDA-RX7-13B-TU...713.m153.l1262
From a shop in autsralia, flange looks really thick on the stainless one, i'm assuming the mild steel one is the same.
Looks like a good deal, off the shelf divided T4 FC manifold that looks to be built pretty well.