Before you remove the sprockets to release the chain, bring #1 cylinder to TDC, which should align the marks on the front cam tower and thrust washer. Then put a dab of paint on the chain and sprocket to further aid you in reassembly.
Be sure to check for chain stretch with the marks aligned - lots of posts on how to do this and this would be a good time to do the chain if needed.
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