I over bought St Louis style ribs and wonder if I should freeze them in their original packing now and Sous Vide them at a later date, or Sous vide them, freeze tem and finish them at a later date.
This could work either way, and in part, depends on how you like to prepare them. Since you would likely cook them low temp for a long time to take advantage of the cooking technique, I would marinate or brine (your preferred preparation),sous vide, then freeze. That way, you would only have to thaw (or re-therm in bath) and finish (sear of some sort) to have a meal ready in less time than the original preparation
Freeze them already vacuumed in the sous-vide bags and thaw them in the sous-vide-tank. Just add some time to your usual time (i don't have values at hand).
I buy meat in bulk, add seasoning plus a little oil (about a teaspoon per steak is plenty), vacuum seal and freeze raw. Then I just pop them into a water bath to cook. You can also sous vide and then freeze. A lot of people do it this way. I suppose it depends on what you want: if you want a quick, convenient meal, sous vide before freezing (good for chicken breast, for example). If you want succulent, delicious steaks, chops, or ribs that you finish off the grill, I would freeze raw and cook all in one shot.
Since ribs are considered a tough meat, they benefit from a long cook. Here are a few tips: 1) For long cooks (more than about 6 hrs), do not salt the meat. Other seasonings are okay but not always necessary, as the meat cooks in its own juices and tends to be flavorful without any additions. 2) Beef ribs do well at 140F for 48-72 hrs. Pork ribs do well at 149F for 48-60 hrs.
Here are sous vide time and temp tables for proteins; this may help you in the future.