Give us some more info:
Is it an HEI (big diameter cap with coil in cap)?
If so, take the cap off and look at the ignition module.
How many pins does it have (probably either 4 or 7)?
If it has 7, is there 5 on one side and 2 on the other OR is
it a 4 on one side and 3 on the other?
What is the number on the distributor (stamped on the casting)?

mike in tucson