Is there a difference in the rear suspension of one having 7 leaf and 2 bolt shackle and one having 5 leafs and 3 bolt shackle? I've never seen this one of having 5 leafs and a little leaf at the rear top shackle bolt.

 

Please start by stating the year and model truck you are asking about.

 

The 7 leaf 2 bolt shackle is a 72 F100 Sport Custom SWB and the other is a 70 F100 bare rolling chassis. I purchased the 72 and was given the 70 chassis. I thought it would be easy to just do a frame restoration then remove my 72 to that one as i don't have alot of room. Everything really looks the same except the rear suspension. I never seen this type with 3 bolt shackle in rear 1 towards the front and a short leaf attached to top bolt pressing down on spring.

 

Sounds like some sort of helper spring setup, but your trucks are newer than most of us deal with since this is the 1948-60 forum. Might try the forum that covers the 70-72 years for better info.

 

Sounds like the one truck has the flex-o-matic spring setup.