H pipe dual exhaust

[dailey]

hi guys,
im up to building the cat back side of my exaust for my torana conversion.
with the space available im stuck with using either a straight dual or H-pipe design.
im using slightly moded uzz31 headers and aftermarket cats (any sugestions?)
The engine is stock.
does anyone have any sugestions on what pipe size, h-pipe size/position/length etc. to use?
Thanks boys