[lxndr]

The Prelude B20 is different from the Civic/Integra B-series motors, the motor tilts back in the engine bay and the mounts are different from the Civic/Integra B-series. The head alignment dowels will need to be drilled out in order to accept your B16 head and you need to tap the block for an oil line in order to run your VTEC head.

You're better off picking up another B16 block, a B18A/B (LS block) or a B18C block. The B16 is one of the best Honda motors ever, the rod/stroke ratio is near perfect meaning it's a great motor to modify for more power. Granted nothing beats a larger motor, but the B16 is designed to be a high reving motor which is how smaller motors make power. This is the reason why the B16 came with a VTEC head, so it could take advantage of the higher rev limit of the block.

Besides, most every Prelude owner I've met says the Prelude B-20 is the worst of all the B-series motors.