Is it to possible to find out who of those came through the qualies? As De Wulf did I think.
From this list,
Filip Dewulf(RG 97), Bob Giltinan (AO 77 Dec), Vladimir Voltchkov(W 00)
John McEnroe is the only other male player to have achieved this(W 77)
In case you are interested, Christine Dorey(AO 78) and Alexandra Stevenson(W 99) are the only WTA players to do the same.
No qualifier(ATP or WTA) in the open era has ever reached a GS Final.