I could not find an adapter to connect my Greg's extruder to my scratch built standard Prusa i3 X carriage so I decided to create one.
This uses 50mm spacing for the extruder and mount holes. The extruder uses M4 and the carriage uses M3. I have added holes for a 40mm fan as well and they are spaced at 32mm.
I printed this in 0.3mm layers with a 40% fill. I may use a more solid fill after I have had a chance to test the durability.