1965 HIPO 273 intake manafolds.. Any good upgrades??

I want duels.. do I have to notch the cross member for the pass side? Or does the 2 into 1 work ok? If so what size?? It's a HiPo 273 with a magnum 270S cam. And the factory 4bbl. I'm using an electric fuel pump and Pertronix II. If I go with duels.. whats the recommended size 2.25" or 2.5"?