10" drum source?

Yes, it's a pretty arcane measurement based on the wheel bolt circle. 1972 was the last year of the 4-inch bolt pattern for Darts. Unless you have replaced the rear axles and the front hubs, you will have the small bolt pattern.

One test you can try -- it is very close to the 100mm bolt pattern common to many European cars.

If your car had been converted to large bolt pattern, that would be 4.5 inch, which is significantly larger than 100mm.