Changing the hot end on my stock Wanhao i3 to a cheap chinese J-head from aliexpress with as little work as possible just reversed original mount and changed two M3.5 screws for longer ones, I had a metal extruder unit so used that but there are many available on thingverse for those that need them. I raised the top bar and gave more clearance attaching by top screw only and used bottom two to mount original extruder bracket, doesn’t affect stability and increases printable height by 20mm. Mounting the fan to shroud I just used 4 small wood screws.

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