It can be and is likely the same. Depends on if the regular chevy truck had the same housing or was a full float axle or whatever. I have over 35+ years in shops and I never swapped gears in a housing. My shops either just installed a new or used differential or I had a specialist that built them. I do know that one of the things I was told to do was to initially start out with the same shim set up as in the housing now with the old gears. With the new, set it up first with those shims and see where the pattern is and adjust from there.
The thing that threw me, is your statement that the noise was after the idler arm install but with the condition of the gears, the noise had to be there before.
