Rear differential mount insulator missing?

I had a rebuilt differential put in my truck a few months ago. I got underneath tonight to try to read the axle tag when I noticed a space where the differential mounts to the frame where it looks like there should be some kind of bushing:



This would be part "4B424" in this pic, which Ford calls the Differential Mount Insulator (Rear):



Here is the entire schematic for context:
Rear Differential Schematic

Would someone be kind enough to crawl under his truck to verify? Or if any of you with experience happen know offhand, please chime in.

Yes, it was missing. This was the same shop that put a 3.73 LS rear end in a truck that originally had a 3.55 open.

I wonder if that part would work as a replacement for the front axle bracket on a 2nd Generation.