First of all, did you do anything with the head while it was off? A head that's been overheated needs to be planed at a machine shop. This means they take off a little metal to make it flat again. If this wasn't done, you need to do that. The head could be sufficiently warped that compression pressure (cylinder pressure) is blowing straight into the water jacket. IF you want to prove this before tearing it down again, you can do a leakdown check to prove what's leaking to what- but it sounds like a pretty clear-cut case to me. It's as if you have a blown headgasket again.

When the head is at the shop, they will also inspect it for cracks and check that the valve train is in good shape (they usually are ok).
The one item that is often neglected after an overheat event is the heater control valve. The original ones are plastic and weak. When overheated, they fail almost immediately and cause the same problems AGAIN. Replace yours with the new all-metal type (FCP Groton, who also has headgasket sets for $29).

Good luck with it!
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total