If you use the NSW RVD that has the spec's for the heights for standard vehicles.
Who is doing the upgrade? The NSW RVD has the upgrade specs in there as well. It sounds like Lovells is the one that you're getting, as the RVD has a new GVM of 3800 and Max towing of 4000kg. Double check what your GCM is with the upgrade, because I'm not 100% sure what it is going to be.
Road Vehicle Descriptor Online - [Leaving Land Cruiser Club]
Have a look for who is doing your upgrade, and then go from there.
There is about 100mm difference between the smallest height and the largest height, so bear that in mind. Also on the 3rd page is the wheel centre to bottom of wheelarch dimension for empty and loaded.
If it's Lovells, then they have a good website with all the details on it:
https://www.lovellsauto.com.au/productsLovells AutomotiveLovells Automotive Systems
www.lovellsauto.com.au
On the Lovells RVD it states " MAJOR DIMENSIONS - Height:W/O Roof Rail or Snorkel = 1975mm, W/ Roof Rail = 2015mm, W/ Snorkel = 2040mm " The snorkel will be the Toyota raised air intake that has a join part way up....