Given those proposed spec.
F: assuming you are to use 255/35/20 tires
-5mm clearance from strut and +7mm extension from fender edge
R: asumming you are to use 285/30/20 tires
-2mm clearance from strut and +36mm extension from fender edge
http://f10.5post.com/forums/showthread.php?t=682126
See post # 10 - same width but offset is 45
http://f10.5post.com/forums/showthread.php?t=618392
More discussion on the 20 * 10.5 wheel fitting
However, you are downsize the rear to 20*10 et 37 with same size tires
-6mm clearance from strut and +20mm extension from fender edge