perhaps there is something I dont know about headers but why is it that all of the shorty headers come with such small diameter y-pipes?

I have a set of hedman shorty 1-5/8 primaries an I am trying to mate them up to a dual cat mufflex system (with the cats in between of course) I previously had the heman y pipe cut to accomadate the dual cats but the guy that made it for me had to use 2-1/4 pipe to make that +90 turn.
Ideally I would like to have 2.5 inch mandrel bent pipe come from the shorties and go to the cats. Is there just not enough room by that box frame rail to pull this off?

does anyone know of a dual cat shorty header that has 2-1/2 pipes that connect the headers to the cats? The websites dont ever include that info.
anyone know the sizes of the pipe on the SLP, hooker, hedmann, edelbrock, dual cat systems? any of them?
Thanks. I just dont want to spend 475 on the mufflex just to choke it down before the cats.

 

my hedman dual cat headers have 2.5" pipes going from the headers to the cats. They are of course mandrel bent. Part #68491....got them from JetHot for $500 including shipping.