Location issue for resonators

I can tell you on a customers truck at work with an aftermarket muffler that resonated badly only under load at cruising speed a glasspack before the muffler cured it.

With the super turbo mufflers on my 01 Mustang GT it drones horrible at cruise. I put glasspacks in the tail pipes and......it still drones horribly.

I would not be afraid to try it (especially if that is where you have the most room) before the muffler. In fact on a couple of vehicles I own I will be doing the same when the time comes to change exhaust.