For those of us who’ve owned an E46 three series Compact and see it as a light-weight coupe rather than an odd-looking hatchback, this is an excellent thread detailing a conversion to S54 and M3 running gear. It’s worth reading to appreciate the fabrication skills alone:
https://www.pistonheads.com/gassing/topic.asp?h=0&f=47&t=1749338&p=1
https://www.pistonheads.com/gassing/topic.asp?h=0&f=47&t=1749338&p=1