This should work with stock extruder, OR any extruder that normally fits on the Ender 3. Only tested on the BMG clone. But there is no reason it wouldn’t work.

There are a few reasons for this.

I’ve seen posts where on the Ender 3 V2, the filament is rubbing along the z rod. This will move the extruder to avoid that.

I needed to move my extruder to fit the BMG extruder as well as the anti-backlash. So this made room for it.

I also printed this in PLA to match my machine. PETG is probably better as the motors do get quite warm. But so far, haven’t run into any issues using PLA. EDIT: See Photos, PLA NOT recommended.

It also has the added benefit of allowing you to take the extruder off easily for cleaning/maintenance, and the stepper motor will sit there without falling to the bed.

I also like the access to the nylon gear for the BMG extruder here. Makes it nice and simple.

You will need 4 x M3 cap head screw 8mm - 10mm long as well as 4 M3 nuts to snug up underneath. You could also use a washer.

I added the loom clip to my profile page if interested.

I printed all of these in PLA, and they are holding up just fine. The stepper motor gets quite warm, so, PETG is probably recommended. EDIT: See Photos PLA not recommended.

EDIT: PLA NOT recommended. The motor gets too hot, and therefore deforms the part. It deformed enough that it was adding strain on one of the posts inside the extruder. See pic. That being said, I've added a revision.

If Printing in PLA, at least use V2, or V3.

10/25/2021: Added V2 and V3. V2 contains a simple clearance hole for the gear inside the extruder. V3 has a slot. Personally, I like printing these face down like V1 orientation so that no supports are needed, which can't be done on V3.