Not a bad plan by any means. The only thing I would change would be the Pro Circuit exhaust ... it's not the best choice. For what you are doing, look into a Sparks or even a HMF.
My question is why go immediately to the 460 stroker kit? For the most part, 400EX owners will progress through bores as needed, going from a 400 to 416 to 426 to 440 and then maybe a 460.
As for the Elka's, be sure to be very honest with whoever is taking the build specs for them. Your weight, tire size, riding style, etc. plays a huge role in the setup. Elka doesn't seem to have the best valving from the factory as it is so make sure to provide correct info so it will at least be close.
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2004 Honda TRX400EX (RED)
PEP, Hydrodynamics, Lonestar Racing, Rath Racing, Pro Armor, Pro Taper, ASV, Streamline
2009 KTM 450SX ATV (ORANGE)
Fox Racing Shox, Lonestar Racing, Precision, Houser, Motoworks, Hiper, Fuel Customs