well i had a 84 325e that ran 16.13 stock and 14.91 modified....

so of course im gonna say 325....but what kind of track car? they are both very worthy cars for Auto X....if its drag racing you are looking for, no offense, its not what they are made for...like someone once said
"Drag Racing a BMW is like fishing with a hooker...fun but not what you paid for"