there are a few options, I have used one of these on a cosworth as all it needs is an rs500 rear 5 bolt flange wastegate housing and its then a direct fit


http://www.atpturbo.com/mm5/merchant...&Category_Code=


or this flange can be used on the above housing and your downpipe will just need a v band flange welding on


http://www.atpturbo.com/mm5/merchant...&Category_Code=






then there is this complete wastegate assembly, but it needs a iirc delta flange adaptor to bolt on which will then make it direct fit for your downpipe


http://www.atpturbo.com/mm5/merchant...&Category_Code=




I still don't see why you cant run a gt3071 though, it just needs running at lower boost so it doesn't surge.





I will try and find a link to the 5 bolt wastegate housing I used, as I had one on my saph and it looked like an rs500 rear housing.