The only way you could, is you would have to remap every block to what it is now.
Actually not true, don't give advice if you haven't tried, looked.
*It is totally possible, but beware of the following things that WILL happen if you do this.
**All Gregtech items will be removed from the game/world
**All Traincraft items will be removed from the game/world
**All Solar Panels will be removed.
**Other mods that aren't in the DW20 pack will be removed as well.
**All other blocks should remain the same. They used the same configs/ID setup throughout so you could switch between packs easier.