To sort of echo what Goatman is saying, I believe you must have told that the camshaft has seized. I suppose that's a possibility but it bears further investigation. Anyone who is a regular on this forum is going to wonder how this diagnosis was reached. If the engine cranks but the cam does not rotate (this can be easily observed) it's more likely to be a broken timing belt. This is an easy, inexpensive repair.

Also, to reiterate what Gman has said, the B21F is not an interference engine so the valves will not be bent.

As far as the B230FT goes, no, it would not be as easy as simply pulling one engine and dropping in the other. Even with the normally aspirated engine it would not be this simple. So if this suggestion also comes from the "mechanic" he may not know what he is saying, or he may have dollar signs in his eyes.

Do not just take the mechanic's word for it.

You haven't asked for help in diagosing the problem but you should really see for yourself what is going on. However, if you are unwilling or unable to do so, and the fact that you put the car in someone else's hands suggests this, you are going to be at the mercy of the incompetent, the unscrupulous or both.
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'80 DL 2 door, '89 DL Wagon