What I do not understand is why you would want an aluminum frame on an Old Army.
I had the al frame on my .41 Mag Blackhawk replace with and Old Army frame and like it that way.
I have pondered this ad nauseam a long time ago and came to the conclusion it's unimportant and only a matter of preference.
As usual there are advantages and disadvantages to both. The aluminum ones are lighter and not prone to rust. Balance is also affected. I don't mind the aluminum grip frames. I was not able to find a blued steel new model Black Hawk grip frame or a less common post 1980s blued steel ROA grip frame. It was either stainless or in the white so I went with the blakck aluminum one which is easy to get and more common. There are complaints that the finish chips on aluminum but my observation is that although a coated finish can certainly chip it is strong for hell, certainly stronger than blueing and does not require attention to keep it from rusting although the rest of the gun does. The aluminum frame is known to be a strong and durable alloy as well. I am not sure I want the old army to be any heavier than it is and it balances just fine for me with an aluminum grip frame.
The original blued Old Army used an aluminum XR-3 Red grip frame but sometime in the 1980's they switched to blued steel for standard production models. Blued steel may be a little (that right just a little) stronger, the blued finish would certainly look much better (my opinion it's a matter of preference,) and the balance would be different. Some say the steel makes it less front heavy, I personally don't find it to be front heavy with the aluminum grip frame but balance can be very important and if one prefers the balance of a steel grip frame that is in my opinion what they should get. Despite that the steel grip frame does add overall weight to the gun. The blued steel grip frames cost more.
I went with what was more commonly available, lower priced, more maintenance free, lighter weight, durable enough, and adequately balanced (for me.) I am glad I did. Aluminum was not a deal breaker for me.
Old XR-3 Red grip frames are still available but not as easy to come by (especially blued steel) while the new Black Hawk grip frames are everywhere and less expensive. I doubt the old XR-3 Red grip frames are going to be easier to get and cheaper as time goes by. The option of using a newer more available grip frame means a lot to anyone who would otherwise not have a functioning gun if they can't locate an original XR-3 Red grip frame.
This also means you don't have to be fleeced by price gougers selling original grip frames or wait forever (maybe really forever?) for tuners or gunsmiths to come up with a fix and/or finish the work.
Maybe more so than should be,the average joe often doesn't have the pull, or money to motivate a good pro so of no fault of his/her own must tackle the task himself/herself. I'll share my experience.
You asked.