WLToys 12428 Front suspension Parts. Front left suspension arm (V2 stronger), caster block and steering knuckle to replace the stock parts. The parts are set up for ease and quality of printing (strength). I didn't have to modify any screw holes but your mileage may vary.
Edit: You might want to try PLA. I made a front arm for my Arrma Outcast 4S that has held up well despite being printed in PLA and all I did was crank up the walls, infill and heat.
You can use 3D builder that comes with Windows 10 to mirror the parts for the right side.
The steering knuckle is an updated version of the one that I'm running with better bearing cups. You'll need to do a little trimming with an exacto knife to get full steering range.
The suspension arm needs a little bit of trimming to clear the steering knuckle to allow full range.
There are built in supports in the caster block and steering knuckle that you will need to remove with an exacto knife. I built them with a .2 gap and they printed great for me. I had no trouble removing the supports but your mileage may vary. Be careful, please. (Supports and fill give me nothing but trouble with PETG, so I build them for stuff like this and it saves a lot of time)
I've run mine in -10 Celsius and it has survived light jumping and crashes so far.
As always, use at your own risk.
Feb 12, 2018 updated suspension arm to V2. The original broke on a moderate but high torque impact, destroying the inner hinge bits. The inner hinge is stronger and thicker and I moved down the shock actuator mount hole to make the part thinner and slightly altered the drive shaft cutout.
Wrench to drive or drive to wrench?
MG Chemicals PETG
Printed at 235, 70 degree bed for nice strong parts.