The .40 NX that I examined had much higher timing (exhaust and Bypass) than the 36 and would be tough to tame for stunt IMHO.
The ASP 36 is available from the link below. (they are in the U.K.) I have used these for stunt and sport flying. They are exactly the same as the Magnum sold by Hobby people. These engines have essentially the same timing as the Evo 36 and internal parts like bearings are interchangeable.
The ASP mounting bolt pattern is identical to the Evo and the weight is actually about 10 grams lighter.
I run mine on 5-10% nitro/22% oil (50/50) and use venturi's from .250" to .265" with a PA or ST NV assy
(.157" dia.). Depending on the weight of the airplane I have added head shims to soften the break. The muffler bolt pattern is the same as OS, Evo, and Magnum so you can use those also.
You can even order the engine in CL version from them if you want.
Hope that helps you out
http://www.justengines.co.uk/acatalog/ASP.html