different distributor caps?

I thought I'd replace the distributor cap on my '65 Valiant with a new one I had laying around. The new one was for my '74 Dart with electronic ignition that I never got around to using. When installed, it backfires or tries to spin backwards, as though the timing's way off. i guess this probably indicates so, but are the distributor caps and distributors in general different between the 60's and mid-70s?