I have an Offenhauser 360 manifold on my 440, and it does not have 4 holes in it ,but rather a square hole with a divider running down the middle... and a big notch in the last 1/4 of the divider. I can't post a pic right now, but...can I run any old carb gasket on it for Holley vacuum seondary or Edlebrock Performer carb? Or do you recommend a particular carb gasket and/or spacer? I have a 70'challenger bulge hood with not a lot of clearance with stock dual snorkel.

I had that same manifold on my big block for a while and I ran this gasket. A little thicker than some. Helped keep heat out of the carb IMO..

https://www.summitracing.com/parts/edl-9...ASABEgKTl_D_BwE

Wingmans' pic appears to match the manifold descrip so that would be my choice (all of the gasket is supported by the manifold).