Be a DT400C. They'd be a pretty good 1973 model bike, but unfortunately they're a 76 model...
Basically a DT360A with a different shaped tank and the 400 motor (which is basically a 400cc version of the DT250A motor), and a bigger front brake.
Will have steel rims, but should have an electronic ignition, which is their only real value... I'll swap the electronic ignition for a points one and some cash.