While the full Clearcase package was tested with LabVIEW 8.0, Clearcase LT was not. I am not aware if the LT version installs the required interface that would allow it to work with LabVIEW. If Clearcase LT can be accessed in VIsual Studio then it should work with LabVIEW. Unfortunately, I cannot tell you for sure that it will.
Regarding the visual comparison, Clearcase does not support the required functionality that allows LabVIEW to perform a visual comparison via Tools>>Source Control>>Show Differences. Please see this knowledge base for more information - http://digital.ni.com/public.nsf/allkb/55E773AAA636C69D862570D600728434
George M
National Instruments