There is no difference between the action itself between an ADL, BDL, SPS, or whatever other models there are ... Long story short, it's either a long action or a short action. The differences come in when you go from a blind mag to a hinged floor plate.
If you have a barreled action w/ a blind mag, and you want to move to a hinged floor plate, you can keep your bbl'd action and trigger, but you will need a new mag box, and the trigger guard assembly w/ the hinged floor plate. I"m not certain about the spring and follower, but would think you'd need them too. Likewise, if you're going from a hinged floor plate to a blind mag, you'll need to replace the same parts, but in the opposite direction as described above. From what I understand, it's a fairly simple process.
Brownells offers "Genuine Remington" ADL-to-BDL kits in their Catolog No. 57, with prices ranging from $122.51 to $135.55, depending on action length, finish, etc. The kits include triggerguard with hinged floorplate, magazine box, follower, and spring.
