I had a friend that had a CRF250r and I measured it up whilst on the bike . I don't know if the 450 shock is differant to the 250 shock but the CRF250r shock isn't worth thinking about. Too long and the clevis is wrong.If you have access to used shocks,i was going to check out Honda crf 450 rear shocks to fit on the rear.The length looks good but i don't know if the ressies would clear the frame etc.
Also,late model 700 Raptor shocks look close.
The TRX rear springs would probly have to be fitted.