Hi There,
Not sure if this helps:
I chose to go for an all Metric build and swapped the Z axis pulleys from MXL to
20 tooth GT2-2 @ $1.85 each (GT2 has less backlash than MXL) and then used a
1524mm/762tooth GT2-2 belt for $2.50 all from Robotdigg.
My view was that the location of the 4 pieces of studding/all thread was pretty arbitrary, so long as they were evenly spaced from the center - it all works in my
Sketchup model of the Buildlog 2.x Laser.
They also now sell a
GT2-2 48 tooth pulley for $3.00 and a
202mm/101tooth GT2-2 belt for $0.40 if you also want to convert the Z axis reducer gears to GT2-2, the 48 tooth pulley has a 5mm bore so would need to be drilled out to 6mm or 1/4", I printed one on my 3D printer.
These parts will fit M6 as well as 1/4" SAE threaded rod, so would require no additional modifications to the design.