Bought a used RF1a transfer case while cleaning it up I noticed a few stress cracks around surrounding the input shaft. None of them look too deep and it hasn't been leaking oil to my knowledge, I was intending on swapping my forward shift to a top cause owner before me snapped one of the shift rods and a whole t-case costs less than the conversion. Looking for advice on whether I should just throw the new tcase in there or do a rebuild and swap the rods on my old tcase

 

Looks like flaws in the mold that the case was cast from.
Is there any sign of cracking carrying into any machined surface adjacent to these supposed stress cracks???
If not, this casting is almost certainly sound.

 

I agree with Millball. I’d think if that cracks started after casting you’d see them extend into the machined surface where the bearing sits, but that appears to be fine.

 

I worked maintenance in an Aluminium foundry for 12 years, those are perfectly normal marks to see...basically caused by (so I was told) by uneven freezing of the metal. More common with permanent moulds then sand casting. Likely this was the "cope" (top) side of the mould judging by the gas holes as well.

However at the bottom of picture three the rod at the bottom seems to have a piece broke out of it judging by the rough edge and visible grain structure.

 

I think that's a notch/detent in the shift fork/rod. I think he's go to go.