E3D-v6 hotend on MK8 extruder
For reference, I have the same printer and am speaking from my experiences.

You have two routes you can take with this, but both are effectively the same result - you need to replace the X carriage.

If you want to re-use your existing extruder components you can pull the MK8 extruder off the X carriage and use it as the extruder to drive a bowden configuration, then all you need is a length of PTFE tube and the couplers between the E3d and the MK8 to hold the tube. This is probably the best solution as it takes a lot of weight off of the X-carriage resulting in significantly better print quality, the only downside is that printing with flexible filaments is a lot more difficult with a bowden configuration, if you intended to do a lot of that.

The other option (and the one I took) is to print an entire new x-carriage/extruder assembly. Because the Anet A8 is based off the Prusa and the Z/X carriage assemblies are basically the same as the original Prusa I3 you can just take any design for the Prusa and fit it onto the Anet, I did this with a gregs wade extruder &amp; E3D hotend mount I found on thingiverse.

I didnt look too hard, but if you are adament on wanting to keep the MK8 extruder on the X-carriage and couple it direct-driven to the V6, you can probably find some x-carriage that lines the two up for this purpose (or you could even design one yourself if you are interested in doing so). I didn't look in to this route myself, so cannot give much guidance.