I had a late E36 328 with A/C and now a very early E36 325 without A/C, the 325 needs a radiator so what would I go shopping for to find the one with the biggest core? As I understand it having air con makes a difference but i'm not sure which way around! Cheers, James.
Yeah m3 is 550mm but as you say the air on models have a larger core. I believe the 328 with aircon is 530mm oppose to the 440mm of a 328 without.
In the normal e36 models there are to types. a small one for modells without a/c and a slightly bigger one for the a/c modells. You see the difference at the last picture here e36racing
Aircon ones are slightly bigger but hardly worth the upgrade. Just get an m3 one, and then get a remote expansion bottle for a self bleeding system rather than the cunting bleed screws the side mounted bottles have. Also you can use the "hot climate pack" rad, which is the same as m3 but with a different more compact expansion tank. If you go for an m3 one remember to buy the correct 550mm viscous shroud, and the lower rad brackets as the oem ones don't fit. Only about £35 quid all in.