I've always placed a trolley jack on the middle of the cross head and used a pair of axle stands to support the bottom tube about 2 to 3 inches each side of the crosshead stamping.
Sometimes I've also placed axle stands under the chassis rails.
As well as checking for wear in the kingpins and bushes, check that the nut at the bottom of the kingpin is as tight as it can be, also the two bolts that secure the bottom plate are also tight - been caught out by that!
Arwyn
