Don't know about the part-numbers, but...
That sensation of the truck's reaction to bumps and road-harshness is worth taking note of.. I experienced first-hand what a difference new cab-to-frame mounts make with my '05 crew. Those mounts are important.
In 2012 I had been looking for the source of an annoying squeak-squeak at low speeds as I drove over small bumps etc. I checked the springs and suspension, greased the tail-gate hinge, anything I could think of. None of that worked.
A 355 Nation member (can't recall who) suggested I look at the cab-to-body mounts.
I had never given a thought to those mounts at all.
I had a shop in Milwaukee pull them one at a time, and we found that the inner steel sleeve through which the bolt passes was corroded. We cleaned them up with a wire wheel and applied lithium grease. That solved the squeaking problem and I was really happy. The bolt on one mount though was too rusted and just spun freely when we tried to pull it. So we left it in place for the time being..
Some time passed and I was off other places (working).
In 2014 I was back in Milwaukee and decided that while I had that shop available to me I wanted to replace that one stubborn rusted mount. Recalling how rusted the mounts had all been and how worn the rubber looked, I purchased replacements for all of them.
By then I had about 125k miles on the truck.
I had recently had the front suspension totally rebuilt, including all the soft parts (bushings, shock-mount insulators, etc).
We greased all the replacement mounts before installing them (which you really really should do, applying heavy lithium grease into the inner sleeve of the mount) then replaced them all.
I was amazed how much better the truck drove and handled, just from replacement of those cab mounts. The truck felt new again in the ride-quality and chassis-noise.
Those mounts are an important part of the truck's overall chassis tuning. As you get into the 100k+ mileage you don't realize how gradually the ride-quality diminishes as compared to when the truck is new. The "noise/vibration/harshness" character of the truck just gradually goes to hell over time and miles.
It's the combination of the shocks and springs with the suspension soft parts, WITH the cab-to-frame mounts. They all work together.
That was my experience.
The one mount that was stubborn when we first removed the others... the bolt had corroded into the nut-plate that's welded into the body where the bolt threads in.
That nut is in a pocket in the floor-pan. Putting torque on the bolt pulled the weldnut loose inside the pocket where it's welded into the floor.
The tech (thanks Nick!) had to cut out a little 2-inch-square hole in the floor from inside the cab (it was the mount at the point just forward of the passenger-side kick-panel), chisel the weld-nut out of the floor and replace it.
Lesson learned: in addition to applying grease to the inner sleeve of the cab mounts, apply anti-seize to the bolt threads as you insert the bolt.
(the bolt inserts upward from underneath the frame, through holes in the frame, up through the mount, and into the cab floor... for those who have not looked at them.. )
