Here is some info and pictures about both setups.
Struts, front: Interchangeable only with appropriate strut bearing assembly, bump stops(if used), and dust boots(if used).
Strut mounts, front: Interchangeable only with appropriate strut and removal of factory alignment pin. NOTE: Changes alignment range.
Shock and mount, rear: Interchangeable
Springs, front: Interchangeable only with appropriate strut mount assembly or modification of spring.
Springs, rear: Interchangeable
Anti-sway bars, front: Interchangeable only with appropriate bushings and brackets
Anti-sway bar, rear: Not interchangeable (forum supplied information; reasonable to believe because of dimensionally different rear subframes, differentials, and difference in spare tire well)
Strut assembly pieces in order:
Stock Non-M:
Stock M3:
The M3 strut bearings are mirrored left to right and have an offset strut attachment hole that changes alignment between the M3 and non-M. The non-M strut bearings have a concentric attachment hole and are identical left and right. The M3 strut bearings can be clocked or swapped left to right to change the alignment range; the factory alignment pin must be unscrewed to do so. I am not sure of any long term integrity or accelerated wear problems caused by this, but I have observed no ill effects on two non-Ms with modified position M3 strut bearings.
Original M3 position strut bearing orientation on left strut; reducing camber and increasing caster compared to non-M:
M3 strut bearing rotated 120 degrees clockwise from original position; decreases camber and decreases caster compared to non-M, increases camber and decreases caster compared to original:
M3 strut bearing rotated 240 degrease clockwise from original postion; increases camber and increases caster compared to non-M, increases camber and decreases caster compared to original:
Underside of M3 strut bearings showing they have substantially more material, are designed for much greater rigidity, and a larger, stronger, sealed bearing is used, greatly increasing service life and reducing chances of strut tower mushrooming with the downside being roughly $90 more expensive per strut bearing:
Non-M struts are partially compressed at rest position, fluid can be heard if shaken, and easier to compress. M3 struts are fully extended at rest, no fluid can be heard if shaken, and are harder to compress.
Non-M left, M3 right
The threaded shaft length above the taper is why non-M(left) and M3(right) struts must be used with the appropriate strut bearings and vice versa:
Appearance, ride, and handling of M3 suspension on a non-M: M3 suspension on a non-M looks similar to non-M sport suspension in terms of ride height, but spring rates are considerably higher and damping is much greater as well. There is no noticeable lift in the front relative to the rear as rumored by some people. The ride feels very similar to an M3 meaning much more road feedback and the car follows the road more sharply. I haven't driven any of these cars hard enough to comment on at-the-limit handling.
*Everything here is through actual experience from working on and driving multiple E46 unless stated. This only info only applies to US market M3 and rear wheel drive non-M.
Struts, front: Interchangeable only with appropriate strut bearing assembly, bump stops(if used), and dust boots(if used).
Strut mounts, front: Interchangeable only with appropriate strut and removal of factory alignment pin. NOTE: Changes alignment range.
Shock and mount, rear: Interchangeable
Springs, front: Interchangeable only with appropriate strut mount assembly or modification of spring.
Springs, rear: Interchangeable
Anti-sway bars, front: Interchangeable only with appropriate bushings and brackets
Anti-sway bar, rear: Not interchangeable (forum supplied information; reasonable to believe because of dimensionally different rear subframes, differentials, and difference in spare tire well)
Strut assembly pieces in order:
Stock Non-M:
Stock M3:
The M3 strut bearings are mirrored left to right and have an offset strut attachment hole that changes alignment between the M3 and non-M. The non-M strut bearings have a concentric attachment hole and are identical left and right. The M3 strut bearings can be clocked or swapped left to right to change the alignment range; the factory alignment pin must be unscrewed to do so. I am not sure of any long term integrity or accelerated wear problems caused by this, but I have observed no ill effects on two non-Ms with modified position M3 strut bearings.
Original M3 position strut bearing orientation on left strut; reducing camber and increasing caster compared to non-M:
M3 strut bearing rotated 120 degrees clockwise from original position; decreases camber and decreases caster compared to non-M, increases camber and decreases caster compared to original:
M3 strut bearing rotated 240 degrease clockwise from original postion; increases camber and increases caster compared to non-M, increases camber and decreases caster compared to original:
Underside of M3 strut bearings showing they have substantially more material, are designed for much greater rigidity, and a larger, stronger, sealed bearing is used, greatly increasing service life and reducing chances of strut tower mushrooming with the downside being roughly $90 more expensive per strut bearing:
Non-M struts are partially compressed at rest position, fluid can be heard if shaken, and easier to compress. M3 struts are fully extended at rest, no fluid can be heard if shaken, and are harder to compress.
Non-M left, M3 right
The threaded shaft length above the taper is why non-M(left) and M3(right) struts must be used with the appropriate strut bearings and vice versa:
Appearance, ride, and handling of M3 suspension on a non-M: M3 suspension on a non-M looks similar to non-M sport suspension in terms of ride height, but spring rates are considerably higher and damping is much greater as well. There is no noticeable lift in the front relative to the rear as rumored by some people. The ride feels very similar to an M3 meaning much more road feedback and the car follows the road more sharply. I haven't driven any of these cars hard enough to comment on at-the-limit handling.
*Everything here is through actual experience from working on and driving multiple E46 unless stated. This only info only applies to US market M3 and rear wheel drive non-M.