1964 Valiant "Get Runnin & Drivin"

What do they say, 500 miles then check backlash and change fluids....or is that new gears? I loved them 3.91's behind my 340 on the street. 70 mile Spring Fling drive was a little nerve racking. I got 2.93's for the 225 turbo and a set of 3.55's on deck for the 403.