Hello from across the Channel!
In the good old days, Gitzo pan-tilt heads or 3-way heads were named 'rationnelle', probably because French consider themselves as the grand-grandsons of René Descartes, the inventor of cartesian coordinates, the most rational means to find where you are in space ... ;
Not kidding, a No4 or No5 Gitzo pan-tilt head will probably do the job.
No4 heads have been discontinued for a long time, but there is still one No 5 available on the catalogue, the reference is 1570M for the "low-profile" one.
http://www.gitzo.com/low-profile-three-way-head
I have the smaller model No3 = 1370, discontinued, and too small for a 10x8" camera but this is the same device actually, slightly reduced weight & size.
A guy on our French large format forum, classifieds section, is desperately trying to sell a No 1570M Gitzo head for about 100 euro.
http://www.galerie-photo.info/forumgp/read.php?7,171108
With a No5 Gitzo pan-tilt head you can't go wrong, it can support about 10 kg and older models can be repaired if necessary. The large supporting plate covered with cork is a pleasure to use, and you should use the big (screw+nut) accessory to firmly attach you camera on the supporting plate, prefer the 3/8 model, the bigger one ref. D2271.15
http://www.gitzo.com/3-8-screw
This is actually the best way to attach something if you do not want to use a quick-release plate. The screw is gently screwed by hand throught the head's supporting plate, until it stops inside the camera's socket. Then you screw the large nut from underneath and firmly press the camera's base against the large supporting plate. No risk to damage the camera's thread or camera"s base plate or whatever.
An alternative to the Gitzo No5 3-way head would be of course a large-size ballhead.
I have an Arca Swiss B2 which offers separate tilt movements in both directions. It looks like a big ballhead but you actually have 2 separate, independant, tilting movements that you lock with a single knob. The B2 and its successor the Z2 offer separate friction control and progressive braking when the tilt angle increases, a unique feature of Arca Swiss ballheads.
With a monorail camera, you can easily balance the weight in order to have the centre of mass above the ballhead, so a good ballhead is a good as a good 3-way head to support a 10x8" camera ; but many users find themselves more comfortable with the 'rationnelle' head and its large handles that you operate with boths hands.
The principle of 3-way heads with separate movements has a direct mechanical consequence, the maximum supported load cannot exceed about 10-15 kg, which is already very strong. But a ballhead like the B2 can support ... well, probably 50 kg or more, the tripod will collapse before the head eventually suffers