I strongly suggest you look at this company in Minnesota. I have their speakers in my 62's and 2 - AM original radios conversions to AM/FM with disc players playing through the original radio(it stays looking original but plays AM/FM and other options).
Read carefully what they say about speakers and the ohm readings and buying speakers that are not correct(and don't work).
I get excellent sound out of the front and rear speakers in my 62 Impalas(4 by 10 to fit the original speaker front mount and the correct speakers for the back seat of all Impalas with the speaker in the seat).
SPEAKERS
http://www.turnswitch.com/speakers.htm
Do not buy generic speakers with large magnets.
They provide advise on what to use for speakers and radio conversions and hooking up the speakers.
There prices for their excellent quality speakers are reasonable...
They now have many other options through the original radio if a person is interested in other options.
Radio conversion
http://www.turnswitch.com/radio1.htm
Paul