What year is the 727? There have only been three different splines on the nose of the output shaft over the years. Some planetaries will install on the wrong output shaft only to strip out after a short time. If you want a cheap steel planetary you better find a B van with a 727 from 91-93 to get the output shaft. Then get yourself a steel planetary from a A618 before 94.
I'll check myself when I get home to see if the years are correct.
If your not stripping the splines out now, why worry. A steel carrier will only slow you down.