Just make sure the wattage of the speakers is the same or higher than the origional, higher would be better is the radio has been upgraded or played at loud volumes and this caused them to blow in the first place. It probably does not matter too much if the replacements are 4 or 8 ohm, but best to try and match the origionals. If one speaker is still working you will propably want to replace it anyway to match the new one. Then after that it is just a matter of making sure they fit. I would try a old stereo speaker first, before spending money on new speakers. As said before it could be the radio its self