360 running on 4 cylinders

Easy. Carb problem on one side or massive vacuum leak into one half of the manifold. We had one member here with a cracked intake runner but that would be rare.
Forgot to mention, I hooked up a vacuum meter to it and it was all over the map. I think it's the carb. I've rebuilt the damn thing twice in the last 6 months and I really think it's not going to work out. My cousin is sending my an old Holley 750 he isn't using anymore, so I'll bolt that on and see what gives.