Positive Camber Impossible?

I assume like the others you're actually talking about positive caster? Because you don't want positive camber anyway, unless you actually are running bias ply's. But be careful about your "alignment guys", if they're using the factory specs (which are for bias plys!) they will be trying to give you positive camber. Which you don't want.

Remember too that the ride height of the car alters the suspension geometry. So, just because one car can get a couple of degrees of positive caster with stock bushings doesn't mean yours can if it's not sitting at the same height.

And if you are running radials, you should be looking for -.5* camber, +3 caster (or more if you have power steering and can get more), and 1/16 to 1/8 toe in. Manual steering should still have positive caster, the more you have the more stable the car will be at speed. It can increase the steering effort some, but it's not a huge effect.