I believe that this is the part. On my 300E it was about $180 list from the dealer because it was Saturday morning. It contains the bearing for the fan and bolts to the front of the block. I am not sure about the 320 but it is a common problem area on the 300.
You may in fact find that it is the source of your noise. I thought mine was the water pump and turned out to be the fan.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe