I had a '74 J in the same color. I tried the nicest tort I could find (Pickguardian's) and it didn't look right. Black was the way to go, especially with a rosewood board.
I'd ask Tony at Pickguardian to make a 5-ply black guard - b/w/b/w/b, for the walnut Gibson look, with two white stripes in the contour.