Rear Leaf Spring Identification ??

Hi Folks,

I am trying to ID the springs on my 72 340 Duster. I have seen numbers referenced in other post, and am wondering where these numbers are located on the springs. The springs have 5 leaf packs, and the rear sits pretty high. Currently running 255/60R 15's and the lip of the wheel opening is 28" from the ground. If possible, I would like to run 265 or even 275's to fill up that opening and gain a bit more bite.

Attached a few pics for reference.









Thank much,

Pat