I know from my experience with my '81 380SL that a noisy valve train can indeed mimic bottom end noise. It looks like you have some bad ball studs. The recommendation that I got was to replace a complete side. You should also replace any worn rockers and (God forbid) camshafts.
I recommend buying one new rocker to use as a check.
When you replace the ball studs, you should also check the preload with the special guage and correct it with the appropriate size thrust washers. Since the preload measurement is against the spring, I don't think it matters if the engine has been rotated. You can get the tool from Assenmacher Specialty Tools in Boulder CO for about $40. Mercedes actually now resells their tool for about the same price.
You may also find that the thrust washers are worn where the rockers contact them. On several of mine, simply replacing a worn thrust washer with a good one of the same size restored the correct pre-load.
You should also be aware that the timing chain makes a huge amount of noise if it is loose and it is difficult to tell it from valve noise.
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