They did fill the empty space inside the clamshell more so than the OEM ones do. They are firmer, much firmer than OEM. They fit the clamshell brackets nicely. I ran into trouble on the passenger side getting the clamshell assembly with the poly mount into place, but after awhile I got it in. It took some manipulation and quite a few tries. Each truck will be different when it comes to that. My clamshell was contorted and bent from the OEM mounts being shot for so long.
After all was said and done, I gained about a half inch of height at the front of the motor. This was ideal because the old mounts were so worn that the lift pump was rubbing on the crossmember (causing a fuel leak) and my power steering line was rubbing against the frame on the driver side.
Replacing the mounts was a good move and having the engine jacked up provided me with the perfect opportunity to make replacing the lift pump easier.
New poly motor mounts, new lift pump, new “s-hose” fuel line, new power steering lines, new power steering pump, new belts, new balancer. Took me a few days, and she fought me every SINGLE step of the way but it’s done and I’m happy.