setting autoconf version?

[Louis Munro]

On February 7, 2004 01:41 am, JJB wrote:
> I believe auto.conf  comes with the ports-base category.
> Did you cvsup download it?
>

The way I understand it, the system comes with a particular version of
autoconf but there are one or two other versions that exist in the port tree 
(as of 2/7/2004). 
They can all be installed together because some ports will require one version
or another. My problem is that when I try to build a port the system only
considers the default version and doesn't take into account those other
versions that I've installed. 
So I'm thinking that there must be a way to specify which version of autoconf
or any other such port (ie automake) to use when building...