Wouldnt using the two wires connected to actuate a relay that can handle the current the best thing to do? All that could be hidden from view, then one good adequate guage wire going to one side of the relay to the + on the battery and the other side going to the MSD? Either put the relay next to the MSD, or if the battery is in the trunk, have the relay next to the battery, then you got one single wire running in the engine compartment to the MSD. BTW, trunk mounted batterys make engine bays look SO MUCH cleaner!
EDIT: If this is done, but an adequate fuse in the wire from battery to relay as close to the battery as possible.