turbo 6 bangers post here

I have previously gotten a lot of good info on here about where to start. But as I get closer to gathering the last of my parts I was wondering if I could get some help from you guys.
I am not building a 400hp car, just a simple Turbo Six that will hopefully be in the 275-300hp range with around 10psi boost. My questions regard carb choice. All the blow through carbs are what I would consider over kill in the cfm department for my build. I was thinking something like a 390cfm Holley 4 Barrel, I understand the floats will need changed and an electric choke is out but does it need to be a blow through type carb for a mild build such as this one?
My last question is about secondaries. If I am able to use a non blow through carb will vacuum secondaries function properly under boost? Or are mechanicals recommended?
Thanks for the help and info