I'm putting a Sniper on my 69 340 Cuda. I checked with Holley and a dual plane is OK as long as you cut down the centre divider if present.
This is an Edelbrock Performer RPM manifold (7176) showing how I cut down the divider.

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1970 Superbird 440-6bbl, auto
1969 Barracuda 340-4bbl, FB Formula S auto
1969 Barracuda 6.1 L Hemi, 5 speed, Convertible
2022 Can Am Spyder RTL