I am after some advice regarding the various size options offered by custom chrome. I am going for their option that fits on the Pilgrim manifolds with my 3.5l RV8. they offer various size options. Firstly the four tubes that form the bend at the exit through the body, these can be 38, 45 or 50mm. the side pipes can then be 3.5, 4 or 5inch. My question is are these just cosmetic or will there be an optimal configuration for my engine. I haven't spoken to the guys at custom chrome yet but just hoping to gain some advice first.

From what I can see the exhausts offered by Dave (DB) have 50mm tubes into a 4.5inch side pipe.

thank you.