I appreciate you getting me the picture of your dimensions but it's not totally clear exactly what you have dimensionall. Instead check out the picture I attached that shows the dimensions of the mounts on the Demco # DM5988 that you referenced.
What is the year/make/model of the truck? It looks like a factory rail kit from Ford, GM, or Dodge but I'd need to know what you have to be sure. view full answer...
The Axle Riser Kit - Single Square Torsion Axle # LC382741 provides a lift of 3-1/2 inches and there isn't a version that provides 6 inches of lift. view full answer...
I have attached a photo of the head and hitch ball included with the Curt TruTrack Weight Distribution System, part # C17500.
As noted in the photo, the distance from the center of the bottom mounting hole to the top of the hitch ball is 8-7/16 inches. view full answer...