New datum

[ph_de_fr@…]

I'm trying to work with several georeferenced (tfw) tif tiles (aerial photos) 
using OSSIM/Imagelinker (Win 32 version).
Unfortunatelly I'm missing a datum and its ellipsoïd + appropriate proj+grid 
and I do not see any way to add any new datum
ie  NTF (Nouvelle Triangulation de la France) + Clarke 1880 IGN + LCC 
parameters.
Can you help? Redirect to whom it may concern?

Typical French projections are as follows (from my Map Maker 3.5 projection.ini 
file):

[projection 1]
name=Lambert I (Nord)
projection=Lamberts conformal conic
datum=NTF: France
projection code=62
scale factor=0.99987734
longitude=2.3372291667
latitude=49.5000000000
easting=600000
northing=200000
north parallel=50.3959116667
south parallel=48.5985227778

[projection 2]
name=Lambert II étendu (wide)
projection=Lamberts conformal conic
datum=NTF: France
projection code=62
scale factor=0.99987742
longitude=2.3372291667
latitude=46.8000000000
easting=600000
northing=2200000
north parallel=47.6960144444
south parallel=45.8989188889

[projection 3]
name=Lambert II (Centre)
projection=Lamberts conformal conic
datum=NTF: France
projection code=62
scale factor=0.99987742
longitude=2.3372291667
latitude=46.8000000000
easting=600000
northing=200000
north parallel=47.6960144444
south parallel=45.8989188889

[projection 4]
name=Lambert III (Sud)
projection=Lamberts conformal conic
datum=NTF: France
projection code=62
scale factor=1.000000
longitude=2.3372291667
latitude=44.1000000000
easting=600000
northing=200000
north parallel=44.9960938889
south parallel=43.1992913889

[projection 5]
name=Lambert iV (Corse)
projection=Lamberts conformal conic
datum=NTF: France
projection code=62
scale factor=1.000000
longitude=2.3372291667
latitude=42.1650000000
easting=234.358
northing=185861.369
north parallel=42.7676633333
south parallel=41.5603877778

datum : 
name=NTF
location=France
dx=-168
dy=-60
dz=+320
da=-112.2
df=-0.54738859 (should read df x 10000!)
ppm=0.000
rx=0.000
ry=0.000
rz=0.000
Molodenski=yes
Transform=Molodenski
ellipsoid=Clarke 1880 IGN

ellipsoid :
ellipsoid =Clarke 1880 IGN,6378249.200,293.466021300

If any question, let me know.
Thank you for your help.
Regards