[Coley]

...couple of quick things, this does initially sound like a fuel problem.

That said, are you sure your distributor was re-installed correctly?...and not one tooth out when being re-inserted.
7° is a bit low for a timing set point...even for stock, which is normally 8°....and most guys can set theirs up around 10-12° no problem without pinging showing up.

Back to the fuel, are you familiar at all with the Quadrajet carbs?
It might be worth while to take a saturday morning and remove it from the truck (15-20 minutes) and take it into your workshop and take a quick peek inside it by removing the top air horn.
This is not too difficult and does not take too long to do...simply hand tools, 5-10 minutes with some basic ability and care and you can inspect your primary float chamber to see if everything in there is ok.
This also gives you a chance to thoroughly clean the car with carb cleaner and compressed air.

....just a few thoughts and some input here.

Regards,
Coley