2500HD rear shocks

[Tobofsb]

Hello first time poster here - I have an '02 2500 HD, 8.1/Allison, 180,000+ miles, mostly stock except front leveling kit & 295/70/17's on American wheels. I went to replace the rear shocks today with a pair of Bilstien 5100's I bought a couple years ago when I refurbished the front suspension & added leveling kit.
When I pulled the original Bilstein F4-BE5-6082-H0 & compared to the new one, the old shock was roughly 1.5" longer extended. I checked the 5100 part #24-186742 is correct for this truck.
The original Bilstein part number has been updated to 24-060820. This shock has basically the same extended length as the new 5100.
So, should I use the new though somewhat shorter shock or find a longer one?
Sorry for the lengthy post, hope it makes sense.