Cam towers break for two reasons: busted chain and broken crank. Otherwise, oil failures usually cause the bearing to seize and the cam to snap.

Rotate engine and verify that the cam turns AND the rear of the engine turns. If only the front half does, you have a broken crank and need an new engine (there is almost no chance you didn't do the block in at the same time). This usually results in a chunk out the side, though, plus a terrible racket, so I'd not expect you to overlook that. Usually busts the pan, too.

A broken chain will just sit there are you turn the engine with the crank pulley, and in that case a new set of cam towers will fix you right up after you install a new chain and re-set the injection and cam timing.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!