Well, it depends.
Actually, mopars are somewhat handicapped by the available choices in t-bars compared to a coil spring car that can change rates in 50# increments to get the right balance.
A 1.125 front bar produces 1664# of force. A 1.25 bar will produce 2536# of force, or a whole lot more. Will that combo work, sure, so long as you balance it with the right rear combo.
So, just taking a stab at some numbers here; assuming your car weighs around 3800# with a 58% front weight bias, that front suspension combo would require a rear sway bar around 130# of force per wheel and each leaf spring would need to be around 175#. If you run without a rear sway bar, you need a whopping 212# of leaf spring force to balance things out.
Certainly the car's total weight and its front/rear bias is the key here. Taking 75# off the nose reduces front bias to 56% and the rear spring requirements by around 30# each, or gets you down around where the factor style XHD springs are.
The same deal with a 1.125 front sway bar will allow you to run the XHD leafs with no rear sway bar.
So, to simplify, if you want to run a rear bar, get the 1.25. If you don't want to run a rear bar, get the 1.125. Also, please understand that I'm just guessing at your starting weight here. If your higher or lower, or have a different bias, it can change things a lot.
I'd also add that despite the significant difference in size between frame hung and axle hung rear sway bars, the mounting methods bring them much closer to applied rate. Tyically within 30-35# of each other. This is where the Hotchkis bars is such a sweet design, you can alter its rate with the adjustment holes.