I'm happy to have helped. A few years back I had the exact same problem as you so I researched a bit how toe actually works.


Measuring toe in mm is actually a bit old I think, all the alignment systems I have come across have never used it. It also doesn't really make sense to measure it in mm as toe should be an angle, therefore you always have to check the diameter of the wheels. If measuring in mm the toe value is the difference in distance between the front of the wheels and the back of the wheels. So with bigger wheels this value will automatically be higher while the actual toe (in degrees) is the same.


Some other thing to be aware of is that some alignment systems measure in degrees and minutes but others measure in degrees and hunderds of a degree. For the first the total value should be 0°17', but for the second it should be 0,28° (0°17' x 100/60).


For the castor value I'm not really sure if the 3°30' is actually ideal. On a drift car you definately want more. More caster makes the car more stabile, adds self-centering of the steering and also adds negative camber to the outside wheel and removes camber from the inside wheel when the steering wheel is turned.
But apparently too much caster can make the car understeer. But the 3°30' isn't all that much in my opinion, there are lots of cars running something like 7°00'. I don't know what is ideal for a Sierra setup, I would expect it is something that Ford experimented with though. And with the Group A/WRC cars having adjustable top mounts they could have gone higher in caster value, but still the settings for the Escort Cosworth Group A and WRC said 3°30'. Maybe it's just best to experiment with that.