A guy from this board - Dusty4 - mounted his coils under the carbs on the back of the engine and fed his wires thru the holes in the cylinder head to the plugs. I have a finch box with stock coils. I stole his idea and had to splice the stock wires to some extended wires with splices I got from Tommy.

On other builds I've mounted the coils upside down on the back of the seat post downtubes and ran the wires under the chassis. Had to be careful on the chain side.

I have a couple of coil mounts from the 70's that mount the coils on top of the engine over the inspection cover.