Tar oozing from the ignition board or coils is a bad sign. It means the component is about to fail and the engine will either quit or start missing.
Twins are .7-.8mm.
You should probably look for a spark plug if it doesnt have one..
The proper spark plug gap for a 1980 Chevy 350 Pickup is .045, according to spark plug manufacturer (Autolite, Bosch, NGK) specs.
.024 to .028
.030
.044 inch
35
.045 inch.
.032" good luck
0.35 gap
In the early 1980's in Virginia Beach, VA, there was a hunter horse named Court and Spark shown in VBHSA shows.
.034 inch ( according to motorcraft.com , one of Fords websites , for the 1980 Mercury Capri and 1980 Ford Mustang with the 2.3 liter )