Would that be with the 12.00 x 20 tyres as these give a 10% increase on the 10.00 tyres ? I asume you had to do away with the diff locks with the faster diffs ?
Checked the rear springs on the S26 today, they are identical to the ones on my Crusader 35T tractor, 8 leaves 3.5" wide with a total depth of 7" work that one out. You were right about the wheel spacers, they are 1/2" thick and fixed to the drums with countersunk screws. With 7.50 rims on the inside there is just over 1/2" of clearance between the 12.00 tyre and the spring, tried one of the 8.00" wheel and tyre assemblies on the inner and the tyre is CLOSE but not touching !