Source to locate correct distributor numbers per application?

Working on a 1970 Cuda, 426 hemi, automatic. It has a cast iron dual point distributor with an aftermarket tag(rebuilt?) and no other numbers. Somewhere along the line, someone replaced the points with a Pertronix unit that I believe has gone bad. Pertronix can't do anything without the distributor number. What would be the correct part number for the distributor in a 1970 426/auto Cuda?