I know Racing Beat did an S5 T2 swap into a miata . The mounts aren't that hard it would be about making th tranny fit well .

If it was me I would just go haltech on it anyway .

So lets say 275 or so RWHP in a Miata That sounds about right with bolt ons . With a TO4R or an equivalent should be good for 400RWHP easy .

Miata's are Auto-X/Drift cars though it needs under 300RWHP and a somewhat useable powerband or that bish will just light the tires .