what single plane manifold for 360 magnum?

I know. I am not having much luck with this engine. Chasing lifters not pumping up for 2 years with 3 cams and 4 sets of lifters. So I have gone solid and now still having issues. Even the local engine builders and tuners cant find my issues. LOL
I am coming to the USA for the 1st time for a family holiday in January. I think I might look out for a good running magnum then I know it will be ok.

The manifold I was looking at getting is a single plane carby one. But I feel this may not be my issue. I am seeing a Chrysler engine builder this week so I hope he can find the issue
cheers