68x42 is the Original BB30 Standard, using Circlips and 61806 Bearings. 68x46 is the PF30 Standards, using press in cups (46mm Diameter) with bearings installed in the cups. Measure what the ID of your BB Shell is and that will tell you what you need to use.
Unfortunately, Spec's carbon OSBB is a variation on PF30. The bare shell is 61mm wide x 46mm ID, whereas a "standard" PF30 shell is 68mm wide. Spec's press-in cups then space the BB out to 68mm by having a 3.5mm thick flange.
This explains the OP's problem as well.
There's sometimes a buggy.
How many drivers does a buggy have?
So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.http://www.youtube.com/watch?v=GekiIMh4ZkM