The 4" 325/327/329 PD revolvers all shipped with a V-notch rear sight.
After one trip to the range I know it does not work for me
The factory sent me a square notch replacement kit at no charge.
As to the J-frames, I can not recall the factory ever offering a V or U notch rear blade.
Hondo44 has a good plan to make it yourself
As an alternative, you might acquire the larger style V or U notch that you like and file it down to J-frame dimensions. This would only require bluing of the sight's sides
I have been quite happy with the adjustable J-frame sighttes. But then, I never had a adjustable sight J-frame where I could easily change out the front sight. 25 yard head shots on B-27 targets is entirely feasible with the factory supplied sights