I think that you should rather use WGS84 (SRID = 4326) as it is widely used by the GPS system. And better: just check what WGS type you have in the incoming data.
Differences between those two you can find here: http://spatialreference.org/ref/epsg/4269/ http://spatialreference.org/ref/epsg/4326/
Thanks for the pointer Simon, I’ve updated the post. We standardized on NAD83 as that was what most of the datasets we were using came in, but WGS84 looks like a slightly better option.