Howdy, new to the big three!

[Eagle Kammback]

Howdy everybody!
I just got my first vehicle that was designed by the one of the big three. A 1972 GMC C25
I know a little bit about them, but not too much yet. Grew up with my dad being a Chevy guy but only owned Ford trucks and an RX7 since I've been able to remember, so that probably explains why I'm actually an AMC guy. I've owned an 81 Kammback that the original owner put 300k on. My DD for 7 years was an 83 Eagle wagon that I took off the road when I moved to a cold place and there was no floor left. I also bought a 79 AMX 304 4 speed that needs to be rewired and shipped out west.
My DD for the past 3 years, drove her from upstate NY all across the country, was a 1993 Jeep Cherokee. I loved that car, put 60k on her, and a ton of work into making her my own and beefing her up. Then some jackass speeding took her from this

To this (Got to thank God and my Cherokee for surviving this)

This is my AMX

Here is the Eagle (albeit, in 2009)

This is my new truck, and impractical daily, the truck you all wanted to see

350 with a the Muncie 465, AM Only radio and Air conditioning (Does anybody know where I can find the original option list and pricing for these trucks? I'm quite curious. 2 auxiliary fuel tanks in addition to the standard one. I'm quite fond of roll cages and seat belts after my accident, so price depending, I might do the cage, but definitely converting to a 3 point belt. Other than that, I'm going to keep her mostly stock, with a few minor upgrades here and there. I'd like to modify the truck in 1970s period style. Any thoughts or recommendations?
Edit: Oh yeah, since all I can seem to find is for the 2 headlighted Chevy trucks, anybody link me to a thread on upgrading the 4 headlight GMCs, at a minimum the wiring harness?