The lower ball joint should always lead the upper. I'm no expert, but I can't think of any exceptions to that rule.
Puhn's "How to Make Your Car Handle" has a caster chart. Bearing in mind the book is 30 years old, he lists:
-2 Olds Toronado
-1.5 68-72 Pontiac intermediates
-1 75-79 Buick p/s, 75-80 Nova m/s, 71-72 Eldorado, 73-74 Camaro Z-28
-3/4 75-80 Monza, Skyhawk, Sunbird, 71-80 Vega
-1/2 74-77 Valiant, Dart, Barracuda, Challenger m/s, 75-80 Versailles, Comet, Maverick, Monarch
-1/3 70-73 Toyota pickup
Granted none of those cars are much in the handling department.
At the other extreme:
+7 70-71 MGB
+9 Fiat 850 Spyder
I've driven both of those and wasn't much impressed either.
Most of the cars on the chart range from 0 to +3.
My '71 Capri was theoretically +1.75; I got it close to 0 by moving the sway bar (which doubled as strut rods) back with some custom brackets. Self-centering pretty much went away, but steering effort was very light and my lap times improved slightly at the autocross. My wife liked the feel after she got used to it, but it drove some other drivers nuts, particularly the ones who were used to releasing the steering wheel and letting it unwind by itself.