I got a GulfCoast Robotics all metal V6 hotend for my Anycubic i3 Mega, which I thought was similar enough to the E3D V6 that I could use steddyman's spacer. Not so! The pneumatic fitting for the bowden tube protrudes more on the GulfCoast V6 than on the E3D V6. So I created this spacer.
It should position your GulfCoast Robotics V6 hotend at the same height as the stock Mega hotend.
You will need longer M3 cap screws to install the spacer. I used 20mm long M3 screws, and they fit well.
NOTE: ADJUST RETRACTION! I've been printing with this hotend for a few days now, and noticed I would get clogs when printing PETG. It didn't happen with PLA or ABS, only PETG. I believe this was because my retraction distance using PETG was set much higher than other materials (5mm). I turned my retraction distance down to 3mm, and no more clogs! It seems like if your retraction distance is too high, it pulls hot material into your cold zone, and causes a clog. Just an FYI, YMMV.