All of your suspension components, especially the panhard bar, should be mounted with the car at ride height with the engine and tranny installed to simulate the weight of the car when it is finished. Once you have all the weight in the car and it is supported by the tires and wheels, or jackstands under the axles, have a couple of real heavy duty guys bounce the car real good to settle it in. None of the bolts locating the suspension should be final torqued until this is done. The thru-bolt on the spring does need to be tight and should be a lock nut with blue thread locker to secure it.

Ask away on your questions, beats the heck out of making a mistake that could become hazardous to you and or your car later!!!!!