My crystal ball support license has lapsed so I can't see into the dash in your truck.
Without input from you I don't know exactly which ones you have so I can't comment on specifics just general info...
AXXESS talks to the steering wheel control buttons.
https://axxessinterfaces.com/product...s-instructions
PAC is the chime replacement. Since the T800 uses GM Class II databuss it could be Model RP3-GM11
These provide accessory power to turn the radio on with the ignition and off when the ignition is switched off and the driver door is opened or the ignition has been switched off for 10 minutes... as well as replacing the warning chimes that the Delphi radio originally provided.
https://pac-audio.com/products/radio-replacement/
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1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8
RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.