Ok so i had been looking around for this a little. I had searched on here before with no solid results. Found this info over on BimmerForums
E36 Speaker Sizes Basic:
Kick Panel: 5.25" Midwoofer
Door: 2.5" Midrange
Rear Area: 4"
Standard:
Kick Panel: 5.25" Midwoofer
Door: 2.5" Midrange & 1" tweeter
Rear Area: 4" and 1" tweeter