Primary size and length on SC engine

I finally bit the bullet (well really swallowed the whole gun) a bought a F1x rev front mount Procharger for a 400 low deck stroker build.

My plan is a 470 blow through pump gas engine street engine. My build has some gaps- mainly a short block but I do have a block I was using for mock up and want to start making the headers for the new build.
I had started making them for a 517 N/A motor but now after the new acquisition I am worried my 2" primaries will be to small. The original plan was 2" to slip on merge 3.5 to 3" pipes to Borla multi cores. The total exhaust would be about 6' long.
Now my worry is the 2" will be to small and so will the rest. Every search I have made here any other places has yielded mixed info. some say as big as you can fit to using the same size as N/A.
Any ideas?