tryin to break in new engine, ruff idle

PS - Yes I have the orange box screwed to firewall after scraping off the paint to make good contact.

Also - Both Inertia and Dodgefreak have gut feeling its the carb. I'm getting the same feeling too now. I did some research on it: its a 4180 model made for motorcraft (ford) in the early 80's mustangs. It is known as an "emissions" carb.