Since the motor runs, the relationship between cams and crank must basically be right.
The marks on the cam gears aren't on the gears but are on the washers behind them. They can be put on 180 deg different but that isn't likely the problem.
Since the cams only move 90deg when the crank moves 180, switching the cam markings 180 would take the crank 360. I have seen it happen a number of times where one cam was installed 180 out due to the washer thing.
Looks to me like the crank gear must be on wrong.
The original question was in reguard to chain stretch and I can't go along with what was attempted to verify stretch. The marks on the cams and stands are suitable for getting the gear on correctly as each gear is 18 degrees. They are not accurate for gauging precise cam timing nor stretch even if they were accurate. They might give a qualitative view if one knew exactly where the gears lined up when the chain was new, but the wear on the gears is not fixed when the chain only is replaced.
The proper method of gauging cam timing is with a dial indicator off valve movement. The indicator is set upon the valve retainer and the engine spun until 2mm of valve movement has taken place. At this point the degrees are read off the crank and compared to a standard in the TDM (Technical data manual).
When such a measurement has been made an old chain often has 10-14degrees of retard on the right cam. A new chain probably will only get it back to 3-5deg due to gear wear.
Offset woodruf keys allow this to be corrected to less than two degrees.
Bosch Master, ASE Master, L1
33 years MB technician