out of commission, cant drive my dart anymore

I have a stupid question about the lower control arm..The pivot shaft attaches the control arms to the K member but the pivot arm is just lightly pressed into the LCA bushing, so when tightening the nut on the pivot shaft, what keeps the whole shaft from spinning?

The hole it fits into the K-frame is a tight fit, that's what holds it as you torque the nut down.

I'd highly recommend getting an adjustable prop valve if you can afford it, the factory prop valve kinda sucks it gives too much pressure to the rear brakes IMO.