"If the PVL coil is supposed to be a replacement for the coil on the left, the biggest favour you can do the PVL coil is use the clamp from the bigger coil, put a layer of rubber (cut from an old inner tube?) between the coil and the clamp, tighten the screw and nut through the circular holes in the clamp with thumb-'n'-forefinger only on the screwdriver, bolt the clamp through the slotted holes with thick rubber washers between the clamp and whatever you're bolting it to ... don't let anything else on the bike touch the coil case ... and use the clamp around the PVL coil as a small flower-pot holder or similar ..."
That's exactly what I did, using an old rubber battery strap so that I could use the existing clamp on the Enfield's downtube where the coil is mounted.
I have no idea about the history of Lucas coils - I just followed Hitchcocks' recommendation, and the PVL unit worked perfectly.
I haven't tried the flowerpot suggestion though.