Combining NP231's

I am combining 2 np231's One has a crazy loose chain but shifts one has new seals and a new chain but doesn’t shift into 2wd. once I take the t-case out of my jeep I will be stranded so want to make sure I have everything I need before I start.

Things I think I need...
basic tools
Oil seal remover
Good snap ring pliers
a few quarts of ATF

I assume I will just pull the new chain out of the one case and put it into the other. I thought about a full rebuild but really don’t want to wait for the rebuild kit to come in the mail to be mobile again.

Anything else I should get/think about while doing this?

Thank you in advance

Any seals that need to be removed will need to be replaced.

Most the seals I can get from NAPA?