The reason for twin pipes out the back is the location of the balancing tube. There's no other way. I'll up load some more pix showing you fellas what I mean.
My bros small block 305 Chev in his 40 has the single pipe out the back and sounds like a 6pack. Straight up.




My LS2 in the Holden runs a twin di filippo exhaust system. Sounds awesome! Way way better than a single system. Trust me. The 40's no different.
