{{fullurl:Page Name|oldid=1234}}
And to style it like an internal link, you can use the plainlinks CSS class.
<span class="plainlinks">[{{fullurl:Page Name|oldid=1234}} | your link text]</span>
Now put this pattern into a wiki template like {{oldrevision | title=Page Name | oldid=1234 | linktext=your link text}} and you're in business. :-)
DanB