I have a Bandit - It has same chassis as a Rustler. I called Traxxas and asked what parts are needed to turn it into the Rustler:
3637 Axle front
1654 adapter
3631 front a-arm
3641 caber links
3139 62mm steering rod
any 2.2 truck tire
3655 a-arm
1654 hex adapter
Those are Traxxas part numbers - some you need quanities of two. Look in you bandit manual at the Rustler part since they are the same manual and look where it uses those parts and you can then see what you need quanities of tow of.
For how much it costs, it is cheaper to just buy a new Rustler. The new Rustler is only 30 - 40 dollars more and then you would have 2 cars instead of one.