Kevinski, According to your attachment, the earlier tubes used two shims. But the number of shims doesn't really have an impact on backlash. Given the 3.55 gear set is different from factory, the factory backlash wouldn't be the one to chose, but .008 isn't that much different than .007. I think I'd shoot for the low side of the spec that Chev's of the 40's instructions call for.
