Tamiya TA-42200, new chassis kit with Gear diff II
try places like Rcmarket etc $537 USD
For your TRF 415, i have that as well as a 417, all the parts are interchangeable in regard to the suspension pieces ie: blocks, hubs, arms, so if your 415 has the short arms they haven't changed through the 416 and now to the 417 series. so you dont have to have multiple spares.
TAMIYA - SMOKEM - REEDY