If I were on a tighter budget than I am I would run the 2.5" cast manifold with the J-pipe just you. In fact, I honestly wonder if I went the right direction. You will make quite a bit of horsepower before this setup will be holding you back enough to require a change. Making clifford or langdon shorties into a single turbo header will be a lot more complex and not a whole lot faster.
at what psi would that cause a restriction?
69 Buick Special Deluxe. Intercooled Turbo Chevy 250 @ 15psi on a stock long block. It's kinda fast.
