There is a bit of info in the Assembly Manual.
FIG 3: Here I can see the heat riser built in to the Drivers side EX manifold in the first picture on page 120.
FIG 4: Also the block off plate is shown for the Passenger side EX manifold to block the cross over port.
I can't think of a survivor 69 W31 to look at that has original exhaust....... Anybody?
As far as I can tell the exhaust has no W31 specifics, so a Cutlass with an L74 High Compression 350/310HP would have the same N10 Dual Exhaust as a Cutlass with a W31 350/325HP?
Ryan
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1969 Beaumont 350 Auto White Sold
1969 Beaumont 307 Auto Green Sold
1969 Chevelle SS 396-L35 Auto Blue Sold
1969 Oldsmobile Cutlass 'S' Sports Coupe W31