Thanks for the input Tom!
I ordered their Super 44 mufflers, instead of the ones that came in the entire kit. I didn't want the 5" ones in that kit, wanted to keep it tucked up as high as possible. It's basically a stock LS6, with the original solid cam so I don't expect it to be too loud anyways. In the old Monte I had this motor with Thrush Turbo mufflers, no tail pipes & it wasn't bad. Same exact exhaust in my Camaro with the other LS6, large roller cam, ported alum. heads etc and that thing is just entirely a different beast.
As far as hangers, not a big fan of the hangers provided in the Flowmaster kit, so I also ordered the "Walker" version of the original style muffler hangers last night, same as in the Ground Up kit from the looks of it (bolts to the frame in the 2 original holes). For the rear/tailpipes, I still have the original ones for the '72 dual exhaust that slip over the top of the frame in the very back. They're shot, but I'll use them to see how it works, then get new ones from Ground Up that are replicas of the originals if I like how they fit. Worst case, I'll make something up with a combination of the parts on hand (in stock, lol) & a welding machine .
Thanks again!