Will not fit 2 DIN size units...E36 has one DIN with a big fakaroo (technical term) below the computer. Best you could do is halfaDIN down there. I know, I have one...still hoping for a tuner too.. heard they were a tough fit with the empeg+ tuner

E46 M3...All bets are off as there is no real DIN size mount and having been behind the non M3 E46 dash there is little or no room for DIN units. I have seen it done in 5 series but the stock system was COMPLETELY bypassed and electrical noise was hard to get rid of...

There are some E36 installs here on the board (Sean?) do search on M3 in the install areas