Just did the job: ended up taking both mounts off, doing one at a time. I actually found the left side (passenger side) mount easier to do as the other one had the injection pump terribly in the way. Vibrations are way better now. Will do the rear mounts in future as well as the rear of the truck is still vibrating more than it used to. The Glencoyne rubbers are much softer than the ones the rebuild company had put in. I could actually more or less compress/move the middle rib of the rubber with my thumb, which was impossible with the hard old ones. Can really recommend the upgrade!
Thanks for your replies.