E36 conversions need the E36 M3 3.2 control arms to bring the wheel forward or offset bushings so the wheel will be centered in the wheel well. Also coilovers are needed because the E36 springs are too big.
In the rear the E36 drive flanges look like they go straight on late (post 9/85) E30s, but the mounting face is 11mm inboard compared to stock E30. The height difference in disc rotors(E36/E30) is 8.4mm so a spacer may be needed either on the caliper mount or behind the disc brake. E36 compact flanges are 24mm wider than E30, fine if your going with the E36 setup in the front, the wheel offset will be the same, but it won't if you have an M3 front and if you want to keep offsets the same... Also E30 M3 flanges for late E30, later E30s have larger rear bearings, but are rather expensive. All the flanges will fit on the drive shafts E36 E30 E36 compact all the same splines. (although the length my be different) E36 compact (not 323ti) have smaller bearings same size as the pre 8/85 E30 so you may need the whole trailing arms.
Although, some find the 5 lug conversion impressive, and some will argue the benefits of the 5 lug conversion. I personally can't justify the cost. Brakes, suspension, drive train, rims and all of the other parts needed for the conversion will cost on average about $3000 and up.