A 235 would have three intake manifold ports. Sounds like your leaks on on the two side ports?
The manifolds might need to be planed by a machine shop, but I would first try new manifold gaskets. At that time see if the mating surfaces of the intake/exhaust manifolds are level to each other - place the mating surface on a flat table-top (or, against the head) and see if all surfaces mate properly.
There are alignment rings for the intake manifold. They are sometimes missing. They do not make a seal but if too much material has been taken off the manifold's mating surface, those rings can cause the manifold to leak (the rings would then need to be made thinner in depth).
