1989, well preserved 4x4, looks like one of the original cab mounts is failing- can't ask for more service than it gave. I have never done this type of job before, can you replace singly with oem or equivalent? Haven't checked dealer price ebay doesn't seem to have any nos about, looking at Energy Suspension- very mixed feedback about nvh.....There is a silicone version I should explore, but they don't make a kit specifically for the GMT 400, later GM's- but I think the cab mounts didn't change much- just an awful price.