Assemble the 36'' hair pins with the clevis' and bushing ends with their jam nuts. Thread these pieces in about half of the thread length and finger tighten the jam nuts. Be sure to use anti-seize on the threads. You don't want to think of what galled threads would mean at this point. The two assemblies must be the same in length. An easy way to do this is to stack one on top of the other and insert bolts in the clevis' and bushing ends. Now tighten the jam nuts.
Bolt the spring assembly and the hair pins to the bat wings. Next bolt the axle assembly to the spring perch on the frame. Measure the distance between the axle and the front cross member at the end of the side rails. Set the axle so both sides are exactly the same. Bolt the axle to the angle iron and clamp the angle iron to the frame. Once I'm satisfied the axle /cross member is right, I tack the angle iron to the side rails. It's very important that this distance is perfect through out the heating and bending of the bat wings. At this point, I remove the spring assembly. This prevents damage and keeps them fresh looking.