Sorry, I don't have a XTZ but did a KYB 48 fork (YZ250) conversion to a XTX just recently.

I own a XTR and XTX (along with about 10 other motorcycles, so I know what I am talking about) and converted the XTX as I have no use for a street bike. To match the additional weight of the XTX I decided to use Hyperpro SP-FO-1368 front and progressive Type 1022 rear springs. The result was incredible. Using a 2-1 exhaust I ended up with 310mm clearance.

I took both bikes to a test into the Sahara. As a result I will immediately get rid of the XTR and keep the converted XTX for offroad fun.

P.S.: could well be you have to change the top bearing -> see images.
https://drive.google.com/drive/folde...1U?usp=sharing