You are getting some good answers here SMAC but all is assuming your linkage ratios are correct. Without the proper ratio you may be only able to achieve 1 out of 2 desired adjustments.
1st is throwout bearing clearnce. 1" factory recommended clearance is WAY TOO MUCH, for performance driving. Adjust until bearing spins and back off a bit.
2nd when the clutch engages. This is usually 1/2 to 2/3's up off the floor.
If you can not achieve both, 1 arm on the z bar may need its length modified or the length of the release fork. Changing any linkage rods does not change ratio.
You can run without the overcenter spring. Its only job is to reduce pedal effort from 1/2 way down to the floor, exactly when a 3 finger Borg N Beck needs help.
yeah the 1 inch was refering to the pedal play... don't worry i'm not trying to get an inch at the bearing ! Ram is calling for 1/4 inch there... what i have done is almost exactly what you said... I set the TOB clearance at 0, just touching the fingers (my pedal returns here) then i worked it out from there a few turns at a time until my pedal stuck... backed it up a turn and... the good news is, i have clearance and a pedal that returns... I can't fit my feeler gauge up there to measure it exact but i'd say I'm a little less then the .060 cab mentioned above. There is a slight gap basically just enough that the bearing is not riding on the fingers... not much more. Hopefully that will be ok. gives me about an inch of play on the pedal... but mostly linkage slop.
The z bar ratio could be out like you said but I am assuming the aftermarket pedals have the over center stud on the pedal a touch off (too low), if that stud is mounted higher, over center will happen a touch later in the pedals travel. so more up pull, for a touch longer.
