i have upgraded my original Prusa I3 MK3 with anodized aluminium parts, which has replaced allmost all printed parts.
Also the upgrade is still in process, and will try to document it.
the X-Motor and X-Idler part have been orverworked, due some changes of the current MK3 R3/B7 version. If you have a R3/B7 the rod holes on the x-motor part should have 35 mm instead of 28 mm in the version before, i also made a drill tool for the x-idler, where you can tap afterwards M4 inside, for fintuning the x-rods
the y-belt tensioner is great but you have to add a washer from each site, i have also replaced the pulley, i have a 20 teeth gt2 pulley inside, also the belt is use comes from Contintale and is a high quality belt.
All bearings has been replaced with low noise/friction original Misumi LM8UU bearings
As lube for rods and leadscrew i used with Lithium grease from Kloiber.
As i have seen very good printing results with a Merlin Hotend V3 which uses Airbrush nozzle for printing, i have an idea for an adapter for the E3D v6 Hotend on one Site you have the M5 trhead which goes into the E3D v6 heater-blok and on the other end of the adapter you have a 1.7mm thread for the Airbush nozzle.