I would lift the rear just before you can see the tire.
If you want a muffler that sounds good and gives some backpressure get Walker Dynomax Superturbos.
My dad runs it on his 440 68 Charger R/T and they sound great especially when you mash the skinny pedal.
He runs HP manifolds 2 1/2 non mandrel bent with an H pipe (past the end of the tailshaft) finished with stainless B body tips.
Also the summit brand muffler sounds pretty good as well have them on my dart for now.
And just love your car wish I could see it in person.
What size are your rear tires?