B21A1 engine came in the 90 and 91 Prelude Si as compared to the 90 and 91 2.0Si with the B20A5 engine. The B21 isn't a great engine if it was abused as a child. It has a poor build quality compared to the B20A5 when it came to the cylinder sleeves.
Neither 3rd gen Prelude motor is worthy of swapping into any car to make it a speed machine. The B20 had 135hp and the B21 had 140hp and a little more torque. When in a stock setup the B21 spun faster than the B20 on the highway also.

Chris