Some detective work ahead of ya - like, does the seller know when that issue started (any changes) ?
Will it idle at a higher idle speed ? Runs roughly or smoothly ? Better when engine's up to temp ?
Hopefully the diaphragm base & cap are flat - they're commonly warped.
Need to check floats for corrosion, leaking fuel (won't float), setting.
Squirt some carb cleaner into the carb, especially the bleeds.
Could be a few things: plugged jets, improper idle adjustment...
Worth looking in the distributor & cap for corrosion while you're there.

Double-check your FT, some of that info doesn't read correctly...

Decoder info: https://www.mopar1.us/6971codes.html