What to do? Long or short leaf spring

[kanuck]

I was taking parts from my 2 parts trucks to put on my clean frame that I'm doing from the ground up and ran into a difference.
I have 3 short box frames/trucks for reference and 2 have short leaf springs and the one with the cleanest parts has long springs. The long springs also came from the one truck that had a drop kit on the rear so I took the long rear hanger and the front drop hanger as it was just bolted to the frame.
Moved to the new/clean frame and drilled out the rivets to mount the drop hanger and put the springs in place and they are a couple of inches longer.

So what is the difference between long and short springs? Can't be the years as the frames are from several different years.

Should I just drill out the rivets on the rear hanger and move it back?
What are the Pros and Cons? How does it effect where the long rear hanger goes under the box, as for cutting the box brace?
Springs are 4 long pieces and then one short heavy leaf on the bottom.

Thanks for any info or advice you can give me.....
Hagen