As previously mentioned Challenger said 340 Four Barrel...
I don't recall seeing 340 Magnum on any 70/71/72 Mopars... 73 Charger Rally is the first & only car I recall seeing that badge on... And they were pretty big, like the 440-Sixpack and 426-Hemi badges.... the 440-Magnum/383-Magnum & 340 Four Barrel badges were all small letters..