ok, copied from the 2000 brochure:
W210
style II, 8 J disc x18 ET 31, tyre size 245/40, for front and rear axle B6 603 1007 £434.99
style II, 9 J disc x18ET 35, tyre size 275/35, rear axle only B6 603 1001 £464.97
R129
style II, 8 disc x18 ET 31, tyre size 245/40, front axle only, to 06/98 B6 603 1007 £434.99
style II, 9 disc x18 ET 35, tyre size 275/35, rear axle only, to 06/98 B6 603 1001 £464.97
style II, 8.5J spoke x18 ET 25, tyre size 245/40, B6 603 1003 £963.91
so the 210 and 129 shared the 8 front/9 rear but there was an 8.5 on the 129. Examine the rims but be aware that the part numbers I have listed are * accessory* numbers and potentially not what is stamped into the rims.