* Your vehicle's documentation: The owner's manual or a sticker on the vehicle (often in the driver's side door jamb) should specify the bolt pattern.
* The existing wheels: The bolt pattern is usually stamped on the back of the wheel itself.
* The wheel hubs: You might be able to find the bolt pattern cast into the hub.
Without knowing the specific configuration of your 1970 Dodge D100, I cannot definitively answer your question. You must verify the bolt pattern yourself using one of the methods above. Using the incorrect bolt pattern is extremely dangerous.
