Three digit axle code 1970 Plymouth Duster w/3.55 Suregrip

Hi Guys,

This is my first post on the forum. I am a long time e-body owner who recently picked up a rotisserie restored 1970 Plymouth Duster 340. It is an original 340 4 speed car, Plum Crazy interior, black interior whit a white vinyl top. Black longitudinal stripe and a black rear stripe, Rally car. As the car is only in need of minor details I am now at the point of axle tube and differential markings/ stamps.

Does anyone know what the three digit code on the passenger side of the axle tube would have been? I'd like to order a stamp and get this done before the Canadian winter sets in.

I am not a restorer or anything cool like that just a guy who likes adding fun details to his car.
Thanks!