dmc are the bell housings interchangeable?
B30 bellhousings don't fit a B20/B21/B230 at the engine end. Also, the B30 torque converter is bigger.
The transmission face end of the bell however is the same IIRC, and should still bolt up to the B20 bell via 6 bolts. B21/B23 bell for the BW35 is similar to the B20 BW35 bell, but the OHC bells mount the trans at an angle and use metric bolts.
PS & ETA: The BW55 bellhousing is different to the BW35 bell.