I can only assume that the 560 and 450 look similar underneath. There are frame members just outside of the transmission cutout on the front, just behind the front tires.
I've never put the back up on jacks, so I'm not sure there.
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino