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.
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