Will researching for an article on racing bodies I ran across this ad which is quite interesting. Note they are for Ford or "bastard" rods. Must have reamed out the old bearing part
way through and installed these in the smooth remaining bore of the original babbit.
Many early cars had that type of rod and main bearings.
They depended on the thickness of babbitt, and a 100 percent backing for strength.
I have not seen one of them in a FORD rod, but I've probably only seen about 1500 rod cores...
What I find interesting is they apparently had you "ream" the steel out into the bolt hole area with the jig and reamer they sold you
The big question is, Did it work and for how long?
I am sure it worked as well as babbitt, but I doubt any better
Having been rebuilding engines and doing my own babbitting for years, I cannot see any reason why it would not work as long as it was done correctly.