If it is trying to blow between the #2 and #3 cylinders I would make sure head is flat again. One good overheat will warp it. Maybe clean the head and block, set the head on without a gasket, and see if you can slide a.003 feeler gauge in along the side of the head, in the middle. If it is blowing the gasket where the combustion is being sealed then that's where the coolant is getting in and I don't think the manifold is the problem.