Ben,
With respect to the latest incarnation of your Vitus 979 project, should you not already be familiar with my own Vitus 979 ambitions, you may find it informative to peruse the following photographs as well as the wording associated with same (...you can probably skip any photo designated "COMING SOON"):
http://www.velo-pages.com/
Regarding your quest for a 25.0 mm seat post, MAVIC did not manufacture a branded version of their own until 1989 and those Vitus logo Rubis seat posts similarly did not debut until the very late 1980's. Early to mid 1980's French alternatives left for your consideration would include ATAX, Bador, Huret (...simply a JPR rebranded), JPR, Laprade, Simplex, Spidel (...a Simplex, but with Spidel logo), or Stronglight. For my own purposes, I chose to go with a Stronglight Aero Laprade because I too sought to pursue a "Tout François" theme and because the patented Laprade style head offers a wide range of straightforwardly simple adjustability in conjunction with a very secure fitting:
http://www.velo-pages.com/
The "bad" news is that none of the aforementioned seat posts of French origin are particularly plentiful these days, and are even less so when one limits their choice to a 25.0 mm sizing. Of course, their are ample other vintage appropriate 25.0 mm seat posts of alternate origin to be had out there, the most common of which that jump to mind would be those once produced by the likes of Kalloy, Sake Ringyo, Shimano, and of course 3ttt, Campagnolo, ITM, as well as Gipiemme. If you might be interested, I do happen to have a spare NOS Stronglight Aero Laprade seat post (...with the original steel fixing bolt and NOT the alloy one depicted in the link provided) ... BUT ... it is sized at 25.2 mm, so you would have to mill, sand away, or otherwise reduce the lower extremities of this post to accommodate the ever so slightly smaller 25.0 mm sizing (...a simple thing to do really, which is precisely why I bought it in the first place - but I later managed to source a genuine 25.0 mm version, making this one redundant to my own needs), and it can be yours for $40.00 USD to include shipping.
Yes, your Vitus 979 bottom bracket shell came pre-chamfered to accommodate a MAVIC cartridge bottom bracket, and the particular MAVIC 610 RD assembly you seek to use in conjunction with a MAVIC double would be 116 mm assuming a pre 1989 model 630 crankset as opposed to a post 1988 631 "starfish" crankset which would instead require their 114 mm spindle width:
http://www.velo-pages.com/
Sorry to say, but I have no spares of these with which to help you out.
And finally, as you already likely know, in the event that you are unable to come up with the otherwise missing Stronglight B10 headset parts you seek, Stronglight model A9 headset parts of similar vintage are completely interchangeable ... AND ... I just so happen to have a complete French metric threaded A9 in used but very usable state that I can send your way for $30.00 USD shipped (...sorry, no handy-dandy pictures - but I can always take a few for you if needed).
PayPal preferred - contact me "Off List" if you are interested in either the Stronglight seat post, headset, or both.
Robert "I really need to do a bit of spring cleaning (...if only I could find the time)" Broderick ...the "Chronically Cloudy Clime" of Oregon Portland, USA
> From: kamenjas@gmail.com
> To: classicrendezvous@bikelist.org
> Date: Sun, 21 Mar 2010 00:41:40 +1100
> Subject: [CR] a little Vitus 979 help - WTB 25.0mm seatpost, Mavic BB and Stronglight B10 headset parts
>
> Coolio's
>
> I've abandoned my Vitus 650b Porteur ambitions ... http://www.cyclebucket.com/
> It was just a little "out there" and the ether eventually wore off.
> Instead I'd like to build it up "proper" with some Mavic parts I have
> and keep it Frenchy Chic. Encountered a few hiccups and I might need
> the advice and help of others here.
>
> Firstly, I need a 25.0mm seat post. Something to suit the period would
> be nice. Fluted is welcome.
>
> Secondly, the BB shell looks like it's been chamfered to suit a
> proprietary Mavic cartridge style bottom bracket.
> http://www.cyclebucket.com/
>
> Wondering if anyone has one of these to suit a Mavic (campy style)
> double ... I'm thinking about 115mm in overall length. Looks like one
> of these ... http://www.cyclebucket.com/
>
> Failing that, are there any other bottom bracket options? I have an
> EDCO BB with eccentric cups but it means milling out the BB shell to
> 35mm and losing the threads? I'm reticent to go that route as it's
> alloy. And I'm not sure of the Velo Orange expanding unit will work.
>
> Lastly, to make my project even more impossible I wish to use a
> Stronglight B10 plastic headset ... just because :-p
> Any tips on seating the plastic fork crown race? And I'm missing the
> top alloy threaded nuts .. does anyone have any to sell or can I use
> any top locknut and some kind of threaded steerer spacer. I'd
> appreciate if anyone has one at hand or can provide good pics. The
> below pics show what I have and also a complete set for reference.
>
> http://www.cyclebucket.com/
> http://www.cyclebucket.com/
> http://www.cyclebucket.com/
> http://www.cyclebucket.com/
>
> Of course I don't have to use the B10 headset parts that I have but
> I'm thinking it'd be nice. I would be grateful for a 25.0mm seatpost
> and Mavic chamfer style BB to suit in usable condition. I have Simplex
> shift levers, an erector set derailleur, early mavic cranks, Mavic 501
> hubs and a nice pair of MA40 rims. It'll be hard to make it Tout Mavic
> but I'm too close to turn back now.
>
> Lemme know what you got ;)
>
>
>
> Au Revoir
>
> Ben Kamenjas
> Kensington, Australie