firechaser just went through this last week ,
for bolt on ..the old 2 bolt flange vrsions of the TAil 38 , turbonetics evolution 38 ,or the precision 39 .. not the new style with vband unless you can weld .
he found a tail 38 on ebay cheap because all those gates have since moved up to vband mounting and now has boost back and boost control
you could find knockoff gates on ebay that replace the TAil38
im using the precision 46 on my atr pipe with a large turbo but thats a vband and required welding