My 01 that the sub in the rear like you mentioned.
I removed it and ran the speaker wires into a line converter and mounted my amp behind the panel were the sub once was. I used jl audio subs. Fosgate door speakers and the factory radio.
Installed my “new” bumper today. Also dyed the top and bottom plastics black. Took a gamble on doing the bottom valance black instead of gray but i like the way it looks.
Buy a cheap IAC valve from Amazon. If it works buy a better quality unit. Throw that one in a box for troubleshooting. I have a big box full of different sensors for troubleshooting, comes in handy
Don’t skip on the converter. It will drive a lot better. I6 tb converters are cheap and work great. I’m getting a 3000k stall built at my local converter shop for $500
Got the AN fittings and fuel line for the V8 swap. I also went ahead and got an E85 340lph fuel pump. I didn’t want to cut my basket for a 450 and didn’t like the fact that the hellcat pump didn’t have a check valve.