Melita will correct me if I'm completely off-base, but you may be able to just create an
SRID based on GCS_NAD_1983, and use that for your geographic input. The difference
between NAD83 and WGS84 is pretty small, though it would certainly be worth the effort
to verify that the shift is within your accuracy requirements (keeping in mind that second
precision is ~30m at the equator, you'd probably have to have hundredths of second
accuracy in your lat/lon values before the datum introduced significant error).
- V