Bummer!
I suggest that you pull the head off and make sure it is usable (not cracked too). The pre-1928 four cylinder engines are notorious for cracking near the single exhaust port because of all of that heat being concentrated in one spot.
The '28 engines distributed the heat better by having two exhaust ports. There are other improvements in the '28 engines too, such as push rod covers and more horsepower.
When a single exhaust type Chevy engine died, some folks replaced them with a '28 engine. It is mostly a bolt in affair, but there are a few items that need to be modified, such as where the exhaust pipe meets the exhaust manifold.
Dean
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