You should be ok with the newer fender , you just have to drill 2 holes to make it line up , people do this all the time to update the look of their 08 or older bikes , as far as plate goes , most people switch to the Cycra Stadium Plate for the X , but if your using R clamps , then i believe with little effort you can make the 10 plate work
As far as getting another set of clamps , if your going to do that then i would TRY to find a set of 08 clamps ( the ones with the Honda Dampener mount) they are 22mm offset instead of 24 like all other year R's (up to 09) as well as the X's , i believe the same holds true for the 250R clamps for 08 , they are harder to find , but if you do find them , you will be happier with the steering , it will steer quicker , if your using the bike for tight single track , it will rid the bike of a lot of the push it has ( not all of it as the rest is caused by the weight of the bike)
But if you cant find any or just dont want to wait to find them , then the 02-07 R clamps are usually pretty plentiful and fairly cheap , note that different year R's have different stops and number plate mounting poles (bottom clamp) and mount hole (top clamp) , so you may have to improvise to keep your clamps from hitting the tank during end to end throw , and when trying to mount whatever plate you decide to use (just something to look at when assembling and checking fitment)
The springs will be the same for the R and the X (as long as they are both 450's) , the plushness is from the valving and the fork tubes themselves , also X springs are slightly shorter than R springs (about 10mm shorter) so it can change your Free Sag slightly
By the way , nice looking bike ....and shop/garage