  We present new CO 1-0 and 2-1 observations of the N83/N84 molecular cloud
complex in the south-east Wing of the Small Magellanic Cloud (SMC). While the
2-1/1-0 integrated line brightness ratio (in temperature units) is uniformly
0.9 throughout most of the complex, we find two distinct regions with unusually
high ratios 2-1/1-0 > 2. These regions are associated with the N84D nebula and
with the inside of the 50 pc expanding molecular shell N83. This shell is
spatially coincident with the NGC 456 stellar association and the HFPK2000-448
radio continuum/X-ray source tentatively classified as a supernova remnant. We
explore possible causes for the high ratios observed and conclude that the CO
emission probably arises from an ensemble of small (R~0.1 pc), warm (T~40 K)
clumps. Analysis of the CO shell parameters suggests that it is wind--driven
and has an age of slightly more than 2 million years. We have also used this
dataset to determine the CO-to-H2 conversion factor in the SMC, an especially
interesting measurement because of the low metallicity of this source (~1/9
solar). Surprisingly, after comparing the CO luminosities of clouds in N83/N84
with their virial masses, we find a CO-to-H2 conversion factor Xco only 1.9
times larger than what we obtain when applying the same algorithm to solar
metallicity clouds in the Milky Way and M 33. This result fits into the
emerging pattern that CO observations with high linear resolution suggest
nearly Galactic values of Xco in a wide range of environments.
