Plugs, Cap, and Rotor Button

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I have a 90 OMC Cobra 5.8 351 and I need to replace the plugs, rotor button and distributor cap. What does everyone recomend to do with these? Can I get an aftermarket distributor cap or do I have to get one from the marine place. This is the kind that has 2 screws to hold it in place. I have already replaced the plug wires.