Hey filter996,
these are all the Different Gentoo builds since 2002, anything preceeding that would not be much use to you I reckon. Yes all Gentoo builds are bulit on using the same package management system (called Ebuild)
http://en.wikipedia.org/wiki/Ebuild
* 1.0, 2002 March 31
* 1.2, 2002 June
* 1.4 August 5, 2003 (GRP introduced)
* 1.4 maintenance release 1 September 11, 2003
* 2004.0 March 1, 2004 (versioning changed to four releases a year)
* 2004.1 April 28, 2004
* 2004.2 July 26, 2004
* 2004.3 November 15, 2004
* 2005.0 March 27, 2005 (versioning changed to semi-annual releases)
* 2005.1 August 8, 2005
you can find more on Gentoo here:
http://en.wikipedia.org/wiki/Gentoo_Linux
Hope this Helps,
Jake