Features include six pneumatic stabilizer legs, activated independently and powered by a compressor. Turntable is motorized. Boom up/down is motorized, and hook up/down also motorized.

Overview of the chassis. Three axles are steered. Turntable for the crane turret will sit between the last two axles.
Closer look at the air rams. Notice the air control switches (one per pneumatic ram) above the air tanks. The remaining three switches are mounted on the other side. The wire bundle will eventually come between the two rows of switches.
The gray geared-down motor will power the turntable. Under the yellow box, an old-style black 12V motor runs the compressor. A couple more shots of the base chassis are below.

The boom is quite tall (up to 5 feet). It folds in half at the middle (mounted on hinges, see pictures below), which is quite unrealistic for a crane, but it was an easy solution for me.

The turret contains three motors: two to raise/lower the boom, and one to operate the hook. The boom leverage arms (yellow beams) on the turret fold down during travel.
As you see, the turret also has a lot of counterweight. Notice the stabilizers are down. They help, but cannot actually lift the truck.
Here is the unfolding procedure (done manually). It put a lot of twisting moment on the truck and you can see it lean to the side. Rare: I included my remote control in the picture.
Boom being raised. Due to friction, the motors could not actually start the raising without some manual help. They could be on their own at about 20 degree angle off the ground. See some more action pics below...