I believe the CB dropped spindles widen the track by a 1/4" per side. (around 6mm)
I have also asked myself about the kerscher Discs and was told they widen the track by about 4mm. Though I cant confirm this myself.
I hope this helps...
BTW Welcome to the site!
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WinterJam 2010: Vdub, Surf, Skate & Musis Fest
WinterJam 2010
'I drive way to fast to worry about cholesterol!'
'67 Sunroof Notchback * '68 FI Squareback