While not a quick and easy task, removing the factory Ram Promaster flooring can be done with a little time, care, and elbow grease.
Starting at the back, after removing all the cargo hold downs, we just used pry bars to separate the wood floor from the steel floor.
The floor is glued in with massive blobs of tough rubber adhesive. Here is the pile of floor sweepings:
Sometimes they separated cleanly at the plywood, sometimes the first few laminations of the plywood would stick to the glue.
Be careful not to dent the metal floor with your pry tools, we slipped a 1″ scrap board to use as force spreader so it would not make sharp dents.
We used a paint scraper to remove the glue:
This also took away some paint so we got some spray can touch up paint (talk to a local auto body paint supply shop) to repair the paint.
And now you are ready to install your insulation/sound deadening/flooring!