Robert has sent me the two following pics with measurements taken from his vehicle.
For the guys needing them in metric...done using my handy scale calculator program!
a) Windscreen width: 1250.95mm.
b) Windscreen height: 342.90mm.
c) Hood width (rear): 673.10mm.
d) Hood width (front upper): 381.00mm.
e) Hood width (front lower): 679.45mm.
f) Front plate intake diameter: 146.80mm
g) Grill height: 598.95mm.
h) Grilll width: 520.70mm.
i) Front cross brace: 395.35mm.
j) Lower front plate width: 695.95mm.
And rear:
a) Lower rear width: Approx 1473.20mm.
b) Height from bottom of cab to cab upper joint:
723.90mm CORRECTED...DUH! 
I'll post some pics later comparing the Mirror and IBG 1:35th scale model cabs.
More to come. Thanks for your efforts Robert, I can now sort out which of those kits is closest to the real thing!
Cheers,
Pete M.
