The thread below is a review of my travails in changing motormounts on my 1977 300D. It may prove helpful.
Motor Mounts, yes again
To answer the question on jackstands,,,,,I ran my 300D up on ramps to gain access. Then jacked the motor with about 3 1.5 ft lengths of two by ten between the jack and the oil pan
I also found that I could access all of screws without lifting the engine. It took a little doing but I was able to get it done.
Send me your number via private message and I'll be glad to provide you with my 2 cents worth via phone.