Yep, it's what you have and what you want to build. Why do people build slants or 273's. Because they can. I likevthe idea of a 390. It's an underdog. Everybody builds 408's. 415's not as much because of availability.
As long as it makes sense to the person building it, as long the goal realistically somewhat achievable and know the generally pros and cons I'm down with whatever people want to build, if OP decided on a blown 500 hp 2.2l kewl lets do it :)