It's not those plastic grommets that are the problem.
They're still attached to the cover.
Don't mess with them!
That crud's spewing outa there because the foam's dead.
I can tell just from how loose the cover is fitting.
Don't mess with those grommets!
Especially with an old original cover. Once removed, they don't like to stay attached to the fabric/vinyl once they are reinstalled. The fabric/vinyl just won't stay pinched in between the two pieces of the grommet. They'll continually pull away from the material & end up floating around the head of the seat belts.
That WILL be a major nuisance for as long as you own the truck.
Here's a link to replacement foam.
Shop from thousands of parts and accessories to help you restore, maintain, and customize your Chevrolet, GMC, Dodge or Ford truck or SUV. Keep 'em on the road with the right part, right price, right now.
* Make sure to read the Product Details as there is 2 variations.
I tried to find just cushion foam, but it seems that that is only sold in sets. Cushion and backrest.
Several vendors, all showing the same pic.
Prices range from $289.95 to $$449.00. SMH.
The link posted is the least expensive.
This is a job you can do yourself.
About a 3.5 on a difficulty scale of 10.
I can help you out with the -re-n-re, but if you do attempt to do this, there is one thing you should know before anything else.
DO NOT pull the seat belts through those grommets!
Undo the belts from the floor. It's a torx. Size? I dunno. I have 4 or 5 of the 'right' size. I just call 'em the torx for the seat belts. I've used them so many times I recognize them by sight. By feel. In the dark.
Leave the belts in the seat when it gets removed from the truck.
Leave the belts in the cover when it gets removed from the foam/frame.
The hole for the belts through the foam is plenty large so there's no fighting with that.