Mrs.Clause has ordered me a 21" .357 max barrel for my TC contender. I've been told I can use 357 mag dies by using two spacer rings ?

I use 357 mag dies and have never needed spacers.

Ditto. Just adjust for the longer length.

You don't need spacers, but you might want some 1680.

Yup, std 357 dies and a dittos on the AA-1680. Might want some 200 gr cast bullets if you don't already have them.