These are the RSM weld in subframe connectors for the 1999-2004 Mustang chassis.  The kit comes in two variations:

• Subframe connectors with reinforcing brackets that mount within the OEM lower control arm pocket (torque box).
  

OR

• Subframe connectors without brackets that can be welded directly to the front face of an aftermarket torque box assembly.

These subframe connectors mount through the floor of the car body, and tie the rear lower control arm pocket ("torque box") together with the front OEM subframe channels. 

Key Features:

• 2" x 2" x 0.083" square tube, designed and routed to fit with the factory seat mounting locations and allow the factory brake lines to be retained. 
• The OEM specific rear brackets provide more than double the bearing surface for the LCA bolts.
• The brackets significantly increases the structure of the OEM torque box without requiring full removal of them. 
• The brackets fit inside the existing LCA mounting pocket, which narrows the opening ~3/8" overall - we provide width specific mounting bushings to fasten the OEM 14mm control arm bolt with a 3/4" heim joint (typical with aftermarket control arms).
• Our LCA brackets are made from formed 3/16" thick steel, and are gusseted on the forward side for additional rigidity.  
• To cap off the installation we provide 1/8" thick lower cover plates, that when welded on, tie together the LCA bracket, subframe connector tube, OEM torque box & frame structure.

If you already have upgraded torque boxes, or plan to go that route in the future, then simply order the subframe connectors without the brackets.   Weld these subframe tubes directly to the front face of the upgraded torque boxes of your choosing and complete the rest of the installation the same way as the full kit.

INSTALLATION INSTRUCTIONS

Fitment Notes:

• The OEM fuel lines will have to be relocated due to spatial constraints where the brake lines pass between the body and subframe connector
• The lower control arms must have either heim joints or narrowed bushings to fit within the RSM upgraded LCA brackets - 2.5" maximum opening width available