I see WVE, Standard Motor Products, and Facet listed. All have aluminum not brass contacts. Material is phenolic or polypropylene. Looks like phenolic holds up to heat better and may be a better insulator. Polypropylene has better resistance to cracking.
Any preferences or long term satisfactory results with any of these caps? I will of course be using new wires, .025 gap plugs, and the silicone squirt.