Ok, the K1/K2 part makes sense that it would be for a progressive spring.
I will have to call Racetech and see if they know the source of their factory spring rates, because that is quite a bit of a difference vs the Yamaha factory service manual.
Swapping the TTR and XT springs shouldn't be a problem for travel as you described since they are the same fork. However, I do know what you mean. I have swapped springs in a few bikes over the years and spend a fair bit of time researching the spring rates and lengths so I have a rough idea on what is needed. (spacers, oil level, tire/fork clearance)
An O2 dependent, H2O saturated, carbon based life-form that swims slower than a sea-cucumber.