I have managed to confirm that at least the SSME mounting to the Space Shuttle Orbiter does not have any shock absorber, as shown in this diagram.
The top of the device bolts directly to the Orbiter thrust structure. The bottom bolts directly to the SSME powerhead. The interface is a "simple" spherical bearing. There is no provision for any kind of compliance.
The drawing is from the Rocketdyne Space Shuttle Main Engine Pocket Data Book RI/RD87-142, page 2-78.
This document has more on the gimbal bearing.
The gimbal bearing provides a means of attaching the engine to the
vehicle while allowing the engine to be pivoted (gimballed) around its
two axes. This is necessary in order to point the engine thrust vector
for vehicle steering, in the manner of a ship’s rudder. The gimbal
bearing is bolted to the vehicle by its upper flange and to the engine
by its lower flange. It supports 7,480 pounds of engine weight and
withstands over 500,000 pounds of thrust. It is a ball-and- socket
universal joint in which concave and convex spherical surfaces on the
seat, body, and block intermesh. Sliding contact occurs between these
surfaces as the bearing is angulated. Fabroid inserts located at the
sliding contact surfaces reduce friction that occurs during gimbal
bearing angulation. The bearing, which is installed during engine
assembly, measures approximately 11 by 14 inches, weighs about 105
pounds, and is made of a titanium alloy.
I cropped this picture to show the engine interface area.
You can see the vehicle side of the spherical bearing in the center of the opening. The bolt pattern matches the drawing!
The green pushrod devices are the thrust vector control actuators, the red circles are covers for the holes where the low pressure turbopumps mount.
Edit: info on the thrust structure from here:
The internal thrust structure supports the three SSMEs. The upper
section of the thrust structure supports the upper SSME, and the lower
section of the thrust structure supports the two lower SSMEs. The
internal thrust structure includes the SSMEs, load reaction truss
structures, engine interface fittings and the actuator support
structure. It supports the SSMEs, the SSME low-pressure turbopumps and
propellant lines. The two orbiter/external tank aft attach points
interface at the longeron fittings.
The internal thrust structure is composed mainly of 28 machined,
diffusion-bonded truss members. In diffusion bonding, titanium strips
are bonded together under heat, pressure and time. This fuses the
titanium strips into a single hollow, homogeneous mass that is lighter
and stronger than a forged part. In looking at the cross section of a
diffusion bond, one sees no weld line. It is a homogeneous parent
metal, yet composed of pieces joined by diffusion bonding. (In OV-105,
the internal thrust structure is a forging.) In selected areas, the
titanium construction is reinforced with boron/epoxy tubular struts to
minimize weight and add stiffness. This reduced the weight by 21
percent, approximately 900 pounds.
Finally found a decent picture of the thrust structure. It's from the Dennis Jenkins book Space Shuttle, the 1992 edition, page 140.