Wheel building problem

I've obtained an alloy rear rim for my 72XLCH; the correct Harley one, it came out of a 75 XLCH. Having removed the original steel rim from my bike, and obtained what I am fairly sure are the correct spokes from J.W. Boon ( # 43031-70A) my friend who's doing the wheel build tells me that these spokes don't fit. I should add that he's a trusted guy with 30 years of Harley experience. He thinks that the problem lies with the bend in the spokes being too acute; on JW Boon's webite these spokes are advertised as "metric" which I have assumed to mean that they are intended to fit the Borrani rim.

My friend says that three of the spokes will cross over but not the fourth; hopefully that will make sense to someone on here who builds wheels, as I don't have a clue.

I've contacted Patrick (french owl) who is none the wiser, as we've both worked from H-D parts books and the factory service manual. In the absence of a Bruce Palmer equivalent book for Sporties (oh how I wish someone would write it!) does anyone have any clues as to what's going wrong please?

The metric designation refers to the threads, not the application. H-D changed to metric spokes sometime around '73. They generally have a triangle stamping on the head.
Due to the way the rim is drilled they do not lace like a normal rim. The spokes will cross over AND UNDER, each other to work. The Borrani rim is dimpled and drilled with the holes offset in pairs. In order to line up the inner spokes lace to the offset side and the outer spokes over them to provide the necessary clearance. Both outer sets face the same direction when laced correctly.
Robbie