Little update. After driving the truck for the past couple weeks with the two front seats in and no sound insulation in the back of the cab, i've gone partially deaf. I was amazed at how well the factory contoured rear carpet thingy and bench seat dampens the noise. It has been so damn loud back in the cab I couldn't even have a phone conversation. Granted my exhaust dumps right there and I drive with the cutout open. Covered the entire rear of the cab with Accumat Hyperflex and then covered with carpet that was the closest match to factory as I could find.
Went with a Kicker 10" Sub with built in amp. Fitment couldn't have been better
Using some left over Accumat for random areas on the roof
Got the rear seat in and harnessed up all three.
The cab noise is back to normal now but the big trouble maker is the leafspring squeak. Wouldn't be an issue but the C-Pillar of the cage is tied to the frame inches away from the leafpack mounting point. Sends creeks through the cab constantly. Maybe time for some leafspring tlc...