[MBZ] 1979 240D Time Chain Stretch

[ts]

Have to adjust valves again has it been 20K allready since I did it?  Bought 
a dial gauage and want to test the stretch and timing while I am in there.
Anyone now exactly what size threaded piece with thread size I need  or can 
describe it to bolt into engine to hold the
dial indicator.  I scimmed through the 616 and 617 engine manual quickly  MB 
said something about this makes sence
and would please like to know what piece I need.  Thanks and happy Friday
Cheers Tom Scordato Bellefonte PA