As I remember it, during the mid 90's, Ajax's formation was as below:-
<pre class="ip-ubbcode-code-pre"> Goalkeeper Sweeper Right Back Left Back Centre Back Right Midfielder Left Midfielder No. 10 Right Winger Centre Forward Left Winger</pre>
In fact, I think Ajax have even used a similar formation this season a few times. It's a 4-3-3 with one of the centre-backs pushing into midfield to make a 3-4-3.