force induction or not ?

Yep, cold 85 is right. Why build two engines? I say, make the choice now and stick with it... unless you have the money to throw around for the rebuild later. I mean it's your decision in the end, and if you are gunna run n/a for the next 5 years then I see your plan working out fine, but if you think you're going to wanna switch in a year or two, I would just build the forced induction engine.