10 ohm or 4 ohm speakers what?

[77 lowboy]

i dont want to cut dash in 77 so going to use original am fm radio. when shopping for speakers i was told that original speakers were 10 ohm and all new stuff is pretty much 4 ohm. also told to run 4 ohm speakers i would need an amp or i would burn up output on radio. im not really a electronic guru and just want a decent sounding fm radio please help with any info.