4.2.1 and 3.3.6 X servers coexist?

[Russell <rjshaw@iprimus.com.au>]

Hi all,

On the XFree86 page: http://www.xfree86.org/current/Status9.html#9
some video cards only work with 3.3.6 X servers and others work
with 4.2.1 X servers.

If i put the two video cards in the pc, can i choose
whether to start the 3.3.6 server or the 4.2.1 server
with suitable entries in a single XF86Config-4 file?
Could a two-head or xinerama system run with these two cards?