The spark plug gap should be .040"
.040
The suggested spark plug gap for a 1973 Harley Davidson is 0.040. It is the suggested gap for most of the spark plugs of that era.
It all depends on the model, displacement, etc...
.040"
40
the gap for a Harley plug on a 88c.i. is 30
1.00 mm
.040
35
.040".
HD 6R12
40