These were made with soldered brass tube, brass threaded rod and Traxxas ball ends and hollow balls.
I made shackles that go where normally the rollers sit on the skidplate.
On the axles they're mounted on the tube that normally the servo mount would be attached to. On the top it's just the hollow ball, on the bottom I made a small bracket to not have the ball stick out to far below the axle.
Getting the measurements right wasn't that hard, I started with the upper link between the axle and the chassis, the length doesn't have to be very accurate since the shackle will adjust for it.
The lower link length also doesn't matter since it has a connector on only one end and the other end has to connect somewhere to the upper link.
Finally I added a small triangle between the 2 parts for bracing.
I'm really happy with these, I knocked both out in just a few hours, they look reasonably scale and work fine.