Those are 30 spline inners but only stock 27 spline outers. Basically you get the stronger HP 44 JK ring and pinion, stronger 30 spline inners, but still 1310 series wheel joints, 27 spline stub shafts, small stock brakes.
As you found out, your 27 spline shafts are your current weak link. Upgrading the inner is a good step but still leaves you with a similar strength outer. (stub shafts typically have better heat treating due to their size but still 27 spline). As gill found out, the 1310 u-joint is also running near its limit for 35s.
If you go with that axle as spec'd there are a few options to upgrade the outers for security:
First would be RCVs - $1250 to 1400 (depending on specific application as ARB wants the shaft a slightly different length than OEM locker but the 300m 27 spline would be significantly stronger than even chromo units).
Second would be a 30 spline outer kit like this: https://www.alloyusa.com/alloy-usa-12168.html - $650
Third, Revolution sells a u-joint upgrade kit that goes to larger JK 1350 u-joints for like $950 but would need to be used with specific ball joints and im not sure if they have a 30 spline outer version.
In both cases I would spend the coin to upgrade brakes to something like vanco or a WJ knuckle swap ($1400 for vanco or $500ish with some minor welding and drilling for WJ brakes with brand new brake parts and used knuckles).
Alternatively, you could ask them to customize it and do JK inner C's and shafts with JK u-joints and jk32 spline outers. I have a complete JK 30 in my shop you can take the outers and brakes off for price of some beer. You would be onto 5x5 bolt pattern wheels but I bet your existing rear shafts and rotors could be re-drilled by a competent machine shop for a decent price. I will take some measurements on my JK axle to verify front WMS stays approx the same in the morning.
