I've pulled out an engine with the transmission in a 88 300E without taking the exhaust apart or taking out the studs. However, some of them do come off with the nut as Jeff mentioned.
Never did the job in a 126, but I'm guessing you should have even more room to move the manifold. I suggest trying my procedure since it is the simplest. If it doesn't clear then try to get those studs out by using two nuts.