As my son's 1972 340 Cuda is on the rotisserie , question has been brought up about brackets to support the dual exhaust thru the rear valance.Car came with a support by the shock brace on passenger side and a bracket thats mounted on the drivers side just up from the rear floor. Some people say the brackets are correct others say i need to add the bracket to the floor area. car is not going to be a show car, just want correct supports so we dont have to add at the tail end after bottom is painted Thanks.

Are you trying for a factory correct setup? If so, what you have is probably the later year dual exhaust arrangement & correct. Later years had rear exhaust hangers that mounted to sides of frame rails. Earlier had them in trunk floor. If 100% isn't needed: just use setup for early years. 2 bkts under floor pan area, & 2 on trunk floor.

Here are a couple pictures of my 73 Challenger's exhaust hanger setup. This is the correct bracket for the passengers side in the later years.(original vs Accurate exhausts replacement)


You can see that it mounts to the shock x-member in the upper left section of the picture.


I think your 72 should use the "bolt-on" bracket mounted to the floor pan on the drivers side like the earlier years.(one half of the bracket is on the interior of the car...behind the back seat) My Challenger was a single exhaust car so I added the DS bracket.

In 74, they used the shock x-member hangers on both sides.

As far as the hangers at the back of the car...some used the hangers mounted to the trunk floor to support the mufflers. The later years used brackets mounted to the frame rail. Not sure what you should have on your 72. My 73 had one bracket mounted to the trunk floor on the passengers side. The frame rail hangers might be a Cuda thing.

looks like what you showed. So there are bolts in the rear frame rails that must hold the tips. So i must be in good shape.

I'm not doing an OE job, but i wander if it would better to buy bracket and put near floor for support?