Is anybody Ohm?

[sssteve]

OK, I never thought of this before and maybe it's been metioned but if anybody can enlighten me.I'm restoring my 67 Caprice that has an original AM/FM multiplex with 4 x 6 speakers in the kick panels and 6 x 9's on the parcel shelf.All the original speakers are either missing or are toast.From what I remember I think the GM speakers were 10 Ohms.As far as I can tell all the speakers on the market today are 4 Ohms.What happens when you match your vintage sound system with todays 4 Ohm speakers.Also has anybody ever "modified" an original multiplex system for better sound and maybe a sattlelite/mp3 addition.Electricity has rarely been my friend.