I'm guessing guy used the oem slider connection to have a leak free setup. If the inside diameter of the resonator inlet matches the outside diameter of the sock x-pipe, the muffler camp should work.
The axleback exhaust section is straight , then curves "over" the axle and rear sway bars to meet the muffler.
Charlie Santos show his setup with GT resonators. 3.7L Mustang BBK Headers AFTER Resonators installed - YouTube