Hi Bobby,
Yep, you got it right; to replace the 3-1/8" shackle straps you currently have, use the MORryde kit with the same 3-1/8" shackle size:
- MORryde Suspension Upgrade Kit for Tandem Axle Trailers - 3-1/8" Long Shackle Straps # MR76ZR view full answer...