Was there a more modern transmission that used a steel planetary housing that will fit my 727 out of a 73 C body? If so, will i need a matching annulus/sun gears from it also?

The 47RH diesel trans has a steel front planetary but it won't fit the '73 727 because the spline angle is different. There is (was) a board member who was machining the spline to fit the 727.

I think that's what the lower end CRT/A&A steel planets are (they have better ones too). They are a broached late model planet.

I have always just used the stock 4 gear units --RV trans usually have them but if you need all you can get Rick at A&A is the 727 master of the universe
Think all the others just buy parts from him maybe

Ok. Thanks guys. I thought i could grab a set of steel planets on ebag for a cheap upgrade. Lots on there for the later transmissions.