Craig - Sorry to be a little late to the party, but I recently got a very cool resource from fellow Bolter Bill Hanlon that has a little something on topic for your question. Bill sent me a Canadian 1955-57 Chevy/GMC Truck Parts Catalog that also included a portion of a 1958-60 Canadian Chevy/GMC Parts Book. In the later partial book, it included a "Clearance Lights" accessory listing page which I've attached below. It doesn't show the specific style of clearance marker light you have, but does have a drawing of what looks to be a '58 or '59 Big Bolt with clearance lights installed on the cab center and a bunch on the cargo box behind the cab.
If nothing else, this might be food for thought in deciding your placement scheme.
Looking forward to seeing what you end up with.
