Right... suspension blocks. do two things.
1) allow setting of toe in
2) allow setting of track width
goes (from widest to narrowest)
1E, 1D, 1C, 1B, 1A, 1X, 1XA, 1XB, 1XC, 1XD
there is 0.5deg of toe difference between each block.
For example on the MRE,
1) with B/A on the front (B the front block, A the rear) there is 0.5deg of toe-OUT
On the rear, with XB/D (XB the front, D the rear) that is 3deg of toe-IN
2) For track width change....
XB/D and XB/B both give 3deg of toe-in (on the rear), but the XB/B combination results in a narrower rear track.
Hope that explains it
There is a chart on my website with all the combinations of blocks.