Paul, here are the Category 0 dimensions on my AC620, I wrote this up several years ago for someone else on the Forum. Don't know if it will be helpful or not or if it will even make sense.
Upper arm width center to center 15"
Upper arm length 6" (center of pivot point to center of lift arm link attachment pin)
Lower lift arm width center to center 13.75"
Lower arm length 21" (center of pivot point to center of pin attachment hole)
Upper lift arm pivot point is at a point 10" above and 6" rearward of lower lift arm pivot point
Lift arm links - 12.5", adjustable + or - approximately 2"
Lift arm links attach at rear end of upper lift arms and at a point 5.25" forward of the center of the lower lift arm pin attachment hole
Stay chains attach to lower lift arm at a point 3.5" forward of lift arm link
Top link attachment points are 0.75" and 2" below upper lift arm pivot point (two attachment points offer options for different implements)
Top link attachment points are 1.75" rearward of upper lift arm pivot point.
Upper arm width center to center 15"
Upper arm length 6" (center of pivot point to center of lift arm link attachment pin)
Lower lift arm width center to center 13.75"
Lower arm length 21" (center of pivot point to center of pin attachment hole)
Upper lift arm pivot point is at a point 10" above and 6" rearward of lower lift arm pivot point
Lift arm links - 12.5", adjustable + or - approximately 2"
Lift arm links attach at rear end of upper lift arms and at a point 5.25" forward of the center of the lower lift arm pin attachment hole
Stay chains attach to lower lift arm at a point 3.5" forward of lift arm link
Top link attachment points are 0.75" and 2" below upper lift arm pivot point (two attachment points offer options for different implements)
Top link attachment points are 1.75" rearward of upper lift arm pivot point.