Steve
What are you trying to achieve and with what kind of jack? I really don't recommend using the MMC jack, except in emergencies. If you do have to use it , I would be VERY careful to ensure it has a solid base and good contact with the chassis, preferably with some sort of well secured pad between the head of the jack and where you are jacking
A small trolley jack under the front cross frame tube is good for all front end work.
At the rear , I tend to use the trolley jack under the junction of the chassis and the rear cross member. This means swapping from side to side. You can jack in the middle of the rear cross member, but make sure you use a flat pad on the jack head to ensure it does not mark the crossmember.
If you want to jack up the entire car on a 2 post lift, then use the junction point of the bulkhead crossmember and the chassis at the front and an appropriate junction point at the rear.
