heres your answers
1---the rear wheel bolt pattern is the same on all 4 bikes you mentioned. the 83-85 200x wheels you have to run them backwards on the 250r's and 350x's.
2--- the trx shocks will fit the atc's no problem but the remote resivior hose is a about 5" longer on the trx250r's
3---the 86 atc250r swingarm is exactly the same as the 86-87 trx250r's. you can put a 85 atc one on a trx if your really desperate.
JASON LISKEY
1985 atc 250r ---- finsh line axle,.fmf exhaust and rictor privateer silencer, prm grab bar.
2008 KTM 525xc quad ----- HMF exhaust, HRE chromoly stem,
86 trx 250r --- with after market chromoly frame and everything else done to it
01 400ex --- with 86 trx 250r motor
87 250x + 93 300ex both 350x powered
2 = 86 atc 350x's
86 atc 250r
83 atc 185s --- from retired guy not ridden since 87
Bandito framed 110 with 85 motor and yellow us90 fenders + tank