Putting a 292 crank in a 250, while possible, is rather complex for a first engine. You would be better off with an offenhauser 4bbl intake, the 268 cam, and some shorty headers with 2 1/4" dual exhaust. That would be a nice running little 250 that wouldn't break the bank.

"The first rule of overkill: You can never have too much overkill."
"Overkill is underrated."