My 1972 Duster is set up how I think you want, but not how you are currently planning. It was a factory /6 car swapped to a 340/727/8-3/4 drivetrain. I was going after the Day Two Muscle Car raked stance. Since my Duster already had a BBP 8-3/4 I converted the front to 1973 BBP 11” disc brakes. I followed that up with all new brake lines, master cylinder, proportioning valve, and brake booster to match the 1973 Duster brake system. Then out back I called ESPO and bought the 340 HD 6-leaf +2” leaf springs. This gave me the rake I wanted, but then I opted for safety based on the recommendations of the members here cautioning about stiff rear springs with soft torsion bars and power brakes being potential spin out in a turn and bought 1.03” PST torsion bars. I set my front torsion bar adjustment to factory measurements (2” difference in elevation between bottom of lower ball joint and bottom of torsion bar socket on lower arm). Followed that up with 215/65R15 on 15x7 zero offset wheels up front and 255/60R15 on 15x8 out back. I retained manual steering but with a fresh steering box and new steering column bearings and a 15” Challenger steering wheel. Handling is flat in corners with no sway bars at all and the steering is perfectly responsive. Plenty of room for activities and no power steering to leak, because I don’t care what anyone says, I have never met a power steering system that didn’t leak eventually lol.
I know you mentioned wanting to do this in stages, but I can’t find a reason to do it in stages, gather up all the parts over the next few months and then tear into it all in one shot. Because disc brake upgrade if changing A arms or finding worn out bushings to replace will require alignment. If you swap to power steering that’s another alignment. Adjust torsion bars regardless of replacing them for bigger, another alignment…. All in one shot, one alignment, back to enjoyment.
Edit: Pic of car added at Post #27.
