Others may know for sure, but I don't believe that there was ever an actual amp per say? They had a stereo with what would be kind of a reverb set up etc... (not as familiar with the 69's)

For what you are looking to get out of your system I would suggest getting all the additional components you want to use (amp, speakers etc.) and then either have the stock stereo converted or add a Custom Autosound's Secret Audio
http://www.custom-autosound.com/secretaudio.php
and then you keep the stock unit in the dash (and could leave it set up just as is with the dash speaker if you wanted) and then be able to run the secret sudio with all the other speakers, CD changer, amp etc...

Either way, yes, it will cost a little bit, but it will be out of sight, and you will have the quality and modern components you would like.

Personally, I kept the stock radio in the dash, and installed an Alpine I had in the glove box (bought a new liner to cut as needed) and two amps, X-over, a CD changer and a sub in the trunk, two 6x9's, two 4x6's, adding two tweeters in the pillars, two bass shakers under the front seats.

All for under $400 But it took me about two years to compile everything and to get the parts of the system that cheap. Still working on it...

Start small, dream big!

Brett - 67 Drop Top 455!