The most important thing to remember is that you need to be able to bleed your brakes, so the bleeder needs to be facing up.
To answer your question, the system I'm working on is more in the 2:00 position. With the size of my caliper, there wasn't room any other way. At the 10:00, it wouldn't clear the steering arm, at the 12:00, it wouldn't clear the kingpin. Coinscidentally, the 2:00 position is where the calipers were set up on the 07 van I took them off of.
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