Welcome to the site !!
As far as i know , CRF250L forks are 43mm and XR forks are 41mm , so that in itself would make a direct swap using the forks only , out of the question , as in "bolt on swap" , the other factors would be wheel fitment , etc , as the entire assembly including wheel and brakes , axle , triple clamps , etc , would have to be swapped , so with that said , you could possibly make it work with finding bearings and possibly shimming the stem to make it work , but would you gain enough for the effort ,,,, i doubt the effort would gain you as much as doing a Re-valve on the 250L forks would , Race Tech already has a good kit (you can do it yourself if your mechanically inclined) , or you could send them your forks and tell them what you're looking to achieve and they should be able to do what you want , or guide you in doing it yourself
You would probably have better luck swapping a CRF250R or X front end to the bike with lesser issues if your ultimate goal is adjustability and ride quality , or even if your looking for just physical adjustability , that would be a better place to spend your money/effort than a outdated XR setup , you could get a entire front end on eBay for decent prices and just have to figure out maybe the stem (possibly needing a shim to make it fit) , i believe the stem bearings are the same (not 100% sure) , i know people have done that swap with success , but it depends on your goal , if you want the ability to adjust clickers , etc , you would be better looking into a CRF250R/X swap , if your looking for just a better ride , then the Race Tech kit would be much cheaper and be easier to do/have done and get you decent results