Congratulations!
The NetBSD source repository has not changed source control systems since project
inception - we're still using CVS, and the whole thing can be browsed at
anoncvs.netbsd.org. A bunch of stuff is now "in the attic" (nominally
"deleted" from the repository, but so far as I know that just means it's
not fetched by default with an unadorned "get" command - it's still in the
repository archive).
The history you're looking to collect is available for copy any time.
Erik <fair(a)netbsd.org> (among other addresses)