Just went an read your post again. sounds like your build plan is very close to what my motor has done to it. As far money it all comes done to cubic dollars. Not sure what kind of prices you are getting from your motor builders, but by the time you get done buying all the bolt on parts and then getting the machine work done to the motor you will be in the 6k range. that is unless you can do alot of the assembly yourself. Hell I had over $770 just in Connecticut state sales tax. That's something alot of people don't budget into their build.
I can tell you this from my own motor build experience..........a 300hp 292 is one fun ride and it sounds bad ass! So much so I am in the process of taking off my Brockman Mellowtones for something (lets just say), a little more neighborhood friendly.
P.S. grow a thick skin and just ignore the V8 and LS guys you won't regret it.