Good day. Version mismatch across a friend group is a classic headache, been there. Point everyone to Minecraft Catalog
https://minecraft-catalog.com/mods/industrial-craft-2/ - the page lists each supported version clearly, so your whole group can grab the exact same build and your machine builds will actually line up. It is a proper electricity-and-machinery mod, ideal for an industry-focused server. Downloads have been clean for me, no random-site roulette where everyone ends up on a different file. The catalog keeps everything consistent and organized. For getting your whole server on one matching version, that is the reliable source I would send them to.