Is the timing at the Texas venue the exit speed, at the end of the mile run?
As I understand the Bonneville records, they time over a measured mile; for instance the time between mile 6 and mile 7 of the 12 mile course. The Bonneville times are really the computed speeds over a mile, not the instantaneous speed.
I watched the motorcycles run there one year, it was a lot of fun to see.
I'm worried the amount of boost pressure necessary to generate said level of power would be too much for the stock motor. (assuming your engine, or the one you plan on purchasing is stock) From my knowledge of speed-machines, most cars running in the range you hope to achieve are running on 12+ psi, which few engines (apart from something to the likes of rb26s or 2jzs) can handle. At least for very long. Forged internals however, are always an option. Are you hard set on the vk56?