My father just passed away and all of his property was in his trust, which is less than 1.5 mil.

I understand his home now has a stepped-up basis to it's current fair market value.

In a safe deposit box I found some gold kruggerands. Do these also get a stepped-up basis. I have no idea how I'd find out what he paid for them.

To my knowledge, stepped-up basis applies to ALL assets, which would include the gold coins. Otherwise, there would be no practical way to properly put a basis on the asset.