[Proj] Datum Conversions

[James G Wilkinson]

PROJ4 community,

This is my first post to this list.  I am looking for some help to 
prepare the
necessary files for a three point or seven point datum conversion for use
with PROJ4.  In my line of work (meteorological and air quality modeling),
I rountinely need to perform a geographic-NAD83 (or NAD27) to Lambert
Conformal Conic-datumless (earth as a sphere) conversion and LCC-NAD83
(NAD27) to geographic-datumless conversion.

I suspect that developing these files is by no means routine, but I am 
at least
willing to make an attempt.  Anything that I might develop will be gladly
shared with the community.  Can anyone provide a literature base (web 
pointers
preferred, but I do have access to decent University libraries) on how to
estimate these parameters?

Regards,

Jim