Penetrated body mounts..

[Canadian Rust Bucket]

It is definitely fixable buddy. I did this last summer on my truck, replacing all 4 on my standard cab. Key Parts makes a good replacement. You'd have to look up their part number for whichever mounts you specifically need.

I did the job by pulling the cab completely off the truck, and I wouldn't want to try replacing these with the rest of the truck in the way.

 

[Caman96]

It’s hard to tell from OP’s picture, but I think he’s talking about the rear floor pan under Extra Cab. I looked and don’t see anyone making that part.

 

[Canadian Rust Bucket]

Agreed it's hard to say from the one picture but I know on my reg cab to get the replacement floor pan in that area I bought a new inner cab corner. From a quick search it looks like the ext cab inner cab corner is completely different and would not fix this issue. I am assuming this is the rearmost mount.

Thanks for pointing out my mistake, I knew I'd replaced it but I couldn't find the receipt for that particular piece.

 

[95burban]

Cut a floor section from a truck at the wrecking yard. Or buy a sheet a metal and make it yourself.