Pending the arrival of other parts to continue to advance on the restoration of the bike, I looked at the damper and after taking the measures, it turns out that the damper of 250 CRF 2008 and longer 30 mm that the original CR, so it will be necessary to make a wedge to shorten it to be able to mount it on the bike, the original being largely outdated in technology and especially rod diameter.
I planned to leave it at its original length because it seemed to me that the fork KYB PSF of my 450 CRF 2013 was longer, but after the assets put side by side, they are the same length, so if I leave the 'shock absorber dive, the bike will poke nose (ok it will be super handy like that, but I lose stability in a straight line with the risk of guiding, so not to lose too much race of the rod of the damper, I'm going to climb a wedge (I have it but it's steel, I'm afraid it's gnawing the rod, it's this piece that helped me to make the plan with the odds) and I would then modify the value Race Sag and Free Sag, to balance the bike.