In a comment on this post, Theron was looking for command-line solutions for converting from UTM to SPCS coordinates on a Unix system; I pointed him towards OGR and GeoTrans as possibilities, and he found that GeoTrans offered a solution. But he also discovered that finding the projection parameters for SPCS wasn’t as easy as he thought it would be. He did track down a few using Google, and was good enough to send them on to me:
A simple, unorganized text listing
Links to both a CSV-listing and an Excel spreadsheet
To find the proper SPCS zone for your location, you can use the program described in the above-linked post, or try this website.
OGR which is part of GDAL recommends the Proj library
http://www.remotesensing.org/proj which includes a bunch of projection parameters for state plane in
the file /usr/share/proj/epsg (on a Debian/Linux system) including epsg codes
For example for North Carolina,
# NAD83 / North Carolina (ftUS)
+proj=lcc +lat_1=36.16666666666666 +lat_2=34.33333333333334 +lat_0=33.75 +lon_0=-79 +x_0=609601.2192024384 +y_0=0 +ellps=GRS80 +datum=NAD83 +to_meter=0.3048006096012192 +no_defs
OGR can convert based on EPSG codes (in this example 2264), which if you have a handful of common projections, it is easier to remember a few epsg codes than wacky projection parameters.