Use the '72. The '71 and up used the pump that accepts the wide bushing front drum. I think all the aftermarket drums use the wide bushing.
A heavy duty 727 will have a 4-clutch front drum vs, the 3-clutch, but for safety, a billet drum is recommended and will fit 5-clutches like the Hemi version.
If you have a 3-clutch front drum, and just want a standard 4-clutch drum, it is just a simple swap of parts. A&A lists a reconditioned 4-clutch drum for $75.
The 5-clutch front drum requires the rear drum to be beveled for clearance, or use an aftermarket billet rear drum too.
Don't worry about the number of pinions the front planetary uses, the aluminum splines are the week point. If you have the power to hurt the aluminum splines, then you need an aftermarket steel planetary.
The Trans-Go TF-2 shift kit to reprogram the valve body if you want to maintain the automatic shifting and will need the kickdown linkage. A Manual Reverse valve body is an option, and don't need the kickdown linkage, but need a shifter that works with the reverse manual valve body.
If the front band lever is a 3.8:1 ratio (Ratio is stamped in the lever) then use it, otherwise use a 4.2:1 ratio. I think Cope Racing Transmissions have them for about $25, but it;s been several years since I checked prices.
The standard for racing clutches are the Alto Red Eagle with the Koleen treated steel plates.

Anyhow, skipping to the end, if the stock '72 is in good condition just do the TF-2 shift kit and run it till it starts slipping, Then inspect it and rebuild/upgrade as needed.