Ok, you are already on 2.3.340. That's the Droid X Froyo ROM. To get to Gingerbread, which is Android 2.3, or 4.5.596 ROM, you root using Z4, download the 2 part TBH files, and install Droid 2 bootstrap (hit bootstrap recovery when its installed, it will say success, then hit reboot recovery). This will boot you into Clockwork recovery. Use the volume buttons to highlight data wipe, and the camera button to select. Then go to advanced and choose wipe dalvik cache. This will give you a clean slate to install the Gingerbread ROM. Next, select install zip from SD card, then choose zip. Find the 2 part files you downloaded and install them IN ORDER! If you don't, you can brick your phone and you will have to sbf and start all over.
After you install the 2 part files, you can use the back button to get to the main screen of Clockwork Recovery, and select reboot. You are now on rooted Gingerbread. If you decide you may want to go back to the stock GB ROM from Apex, create a backup in Clockwork by selecting backup and restore, then backup.
CM74DX