Track is the same between stanza and r31.
You need to buy inserts either way.
R31 brakes are a little better if you were planning on keeping the stock brakes. But not much better
Have to run larger wheels on the r31 struts given the same size discs and calipers
Probably have to cut the spring perches off the stanza struts to shorten them anyway
Can fit more positively offset wheels on r31 struts without fitting the strut