Somewhere on a GM / Chevrolet design spec sheet it was written down. There's always a reason things are done a certain way.
The same 6v coil part number is utilized by all GM makes and some of the independents. In all these cases, the orientation permits the shortest possible high tension lead.
1951 Pontiac coil is mounted horizontally angled slightly downward.
1951 Buick is mounted horizontally on side of engine with wires pointing toward the dizzy behind it.
1951 Cadillac coil lays horizontally on top of the intake manifold, behind the carburetor facing driver side.
1951 Oldsmobile coil lays horizontally on top of intake manifold behind the carburetor facing passenger side.
1951 Kaiser 6cyl uses the same 6v coil as GM. Coil is mounted on driver side of engine vertically with wires on top.
1951 Studebaker V8 mounts the same coil on the firewall with the wires on top angled upward.
