I'm the director of two community and technical college libraries- one is Dewey, the other LC. We are going to make the switch to LC next summer, but in the meantime, I'm trying to find out some specifics regarding companies who will clean up MARC records and assign the LC numbers (and possibly produce the new labels as well). Does anyone have suggestions?
Marcive specifically mentions reclassification on their website. I also found Duncan Systems Specialists (that's their page on reclassfication) with a quick Google search though I had not heard of them before.
Coming from a fairly small (≈60,000 items) community college library, I can say from experience that Marcive did a good job cleaning up inconsistencies in our catalog. We weren't moving from one scheme to another, however.