[Proj] Clark 66 projection help

[mike d'ambrogia]

All,

New to the GIS world but having fun so far (not that being new to GIS
shouldn't be fun...).  I've hit my first roadblock on a project that I'm
trying to move over to mapserver and looking for some help.

This is an arcview project that I'm trying to convert to mapserver for
the Forest Service here in Central Calif so I'm dealing with NAD27 and
clark 66 which are apparently favorites of all.  The map raster images
that I have span from UTM 10 into UTM 11 but interstingly they use UTM10
values even if the area in question is within UTM11.   This leaves me
with some really big easting values for some areas on the map, never
seen this before.  I'm wondering how the projection for that would be
different, if at all?

The arcview prj files show the following:

PROJCS["NAD_1927_UTM_Zone_10N",GEOGCS["GCS_North_American_1927",DATUM["D
_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],PRI
MEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Tran
sverse_Mercator"],PARAMETER["False_Easting",500000],PARAMETER["False_Nor
thing",0],PARAMETER["Central_Meridian",-123],PARAMETER["Scale_Factor",0.
9996],PARAMETER["Latitude_Of_Origin",0],UNIT["Meter",1]]

I can't find an epsg code that seems to match up well, but I may not
know exactly what I am looking at either...

I'm not sure where to go next with this, any suggestions on how to come
up with a valid proj.4 projection from the info above would be greatly
appreicated.  

Mike