formula s resonators

How do the repops sound similar to the original?

My Friend that has the repop resonator is running a flow master for a muffler in front of it and it sounds basier (more base) than the original, he is running a 360 74 basically stock hi po motor, with spit fire headers. He used the commando air cleaner and rocer covers. I told him to go duals, but he wanted a more stock looking exhaust.