Voxelab Aquila Dual Extrusion (should also work on Ender 3 V2)

All of the models required to convert your Aquila or Ender 3 to dual extrusion are included here.  The overall process is detailed in this video: 

At a high level:

1. Disconnect and remove the old control board - there are not enough stepper drivers to support a 2nd extruder.  I used an SKR 1.4 and the included enclosure is for that board but anything with 5 or more steppers would work.
2. Install new controller board and get it working with the existing extruder setup - if you install the enclosure on the left side of the printer you may need to re-route some of the stepper and end stop wires and extend the z end stop wires a bit.
3. You cannot use the Aquila LCD with most controller boards.  If you wish to use an LCD an enclosure for the basic RepRap budget LCD is included.
4. Relocate the existing extruder to the top of the frame.  Most bowden stepper mounts would work however if you don't have one, use the ‘Z Motor Mount Untabbed’ model from here: https://www.printables.com/model/239989-two-motor-z-gantry-big-plans-printer-system/files.  You may need to unsheathe and re-route the stepper wiring.  The included cable holder can be used to keep the wiring in the right place.
5. I'm using BMG clones for extrudes however other extruders should work fine.  I mounted both of them as close to the center of the frame as possible.
6. A second spool holder will be required.  A substantial spool holder model is included.
7. Remove the existing hot end assembly and use the included adapter to attach the E3D chimera or cyclops assembly to the Y carriage.
8. Route bowden tubes from each of the extruders to each of the nozzles
9. Use the included Fan Attachment Adapter, Blower Connector, and Blower Mount with a 50mm blower fan for part cooler.

Now you're good, just set up your firmware and slicer for two extruders.