310d line bore

[sd455dan]

From a machinist that makes his living doing this for a living on excavators, earthmovers and specialty equipment. He had a portable line boring business until California 'outlawed' his diesel truck.
I don't know why you find it suspect as it his professional opinion, but it is only his opinion. In essence, beware and do what you want is the bottom line.

Multiple steels have been used

Some backhoes have it cast right in NOT Weldable.

I Thought old Ford backhoes were weldable steel and If they aren't My Old 755 is Screwed because several pieces have been re welded. Come to think of it most of the pieces are factory welded together including the attachment to the swing frame.
Welding Web has a few threads on this and there were pros that did give their opinion and have re welded "certain" backhoes. I do believe there were some they said No way No How and suggested finding good used pieces for repair

Hopefully the Op just needs new bushings and/or some new pins