67' Dart Front Dash Speaker Replacement?

Here is a link to a company that sells new speakers for old cars. They have the Mopar 4 x 10 speakers. If you are using the factory '67 radio you might need to make sure the 3 1/2 speakers are compatible. The 4 x 10 is a 8-10 ohm speaker and the newer speakers are 4 ohm. I have read that the 4 ohm speakers can burn up the tubes in the factory radio. Just food for thought. Here is the link: http://turnswitch.com/speakers.htm