Here is some onfo on the C33 on E36 Frankie's BMW :: 3 Series :: DIY Procedures :: Factory-Look Audio Upgrades
BMW C33 and CD43 Radios
http://www.tehnomagazin.com/Auto-rad...-Connector.htm
I replaced the C33 against a CD43 on my 1998 E36 M3, the amp on my M3 is in the trunk, right side.
I cannot use the original C33 in US specification here in Japan due to different frequencies.