The Bosch tradition website was very useful. You could look up the Busch part numbers for classics and determine the application for a specific part, or look up a vehicle and find the proper part for that vehicle. Unfortunately the website has been under re-construction for many months now. You could send them an email and ask what those spare distributors you have fit, and what the appropriate distributor number is for your vehicle.
http://www.bosch-classic.com/en/inte...zeugsuche.html