I used ProX rod kit and vertex piston in my 2011 250SX (same generation engine).
I bought a used cylinder from Ebay rather than replate my original cylinder. There are a lot of people that change from 250cc to the 300cc, so they sell good used cylinders. The used cylinder was cheaper than repair, and worked well for me.
I estimate my OEM conrod had 400hrs on it before failed. Unless your engine is damaged by dirt, or run without oil, the original cranks last an extremely long time. Check carefully before you waste your money.
KTM250SX YZ125 YZ85 PW80 ZX6 FZX700