One is front driver's side. 8 is rear passenger side. You can also time from number 5, even though it's on the exhaust stroke. The timing light will still find the mark, since they're 180 degrees out of phase. If it's running, you'll have it right.
There is no dwell setting on a 74. It's an electronic ignition system, a Holley gold box, at least on all the IH trucks I've seen with that engine series. The dwell is not a relevant thing with a pulse generator/amplifier system like that. If you open up the distributor and there really are points, and no gold box on the firewall, dwell for a carb'd gas powered V8 is typically 30 degrees. 28-32 is the spec. That being the case, you could start with a gap of .016 for used points and .019 for new. I don't think you'll find points in there, though.
Allan E.
Curmudgeon Extraordinaire
Charter Member, Old Hippie IH Club
Old fashioned binder freak
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