Hi Steve,
The questions in you post are totally important. I have followed them with interest. Here is some more fuel for the fire which I would give the cheesy title: The Mother of All Brackets.
The most technical responders always seem to answer these questions with spring rates and frequency. I am sure their answers are absolutely correct. However, I believe that, BEFORE a spring rate is selected, the suspension can (and probably should) be set so that all the components are centered in their most optimal position. Some setup details we just pick because it looks cool, like ride height and how low the body sits over the wheels to fill the wheel wells. Some setup is entirely restricted by clearance dimensions under the car. And, other things are just a seat of the pants guess. For example........
The range of suspension travel should not allow the tire to rise up so high that it can bump into the underside of the wheel well. The importance of this seem obvious and is entirely a function of dimensions under the car.
Ground clearance should never be allowed to go to less than a certain minimal distance. Who wants the bottom of their car to get beat up by dips and rises in the road. I think most of us just guess at a safe number. After all, most of us (but not all) probably think zero ground clearance is not enough.
When the suspension is at full drop, the rear trailing arms should not touch or bang into the chassis. My trailing arms just got a fresh coat of powder paint and I do not want them skinned up or bent (not to mention the unhelpful rear end steering that might result).
The adjustment nuts on the coil over shocks should be in the middle of their adjustment range when the car is at static ride height. I paid for adjustability and it just seems like good sense to preserve adjustability.
Shock absorbers should have at least 50% of stroke available for compression. I never want my rubber bump stops to be an active part of my daily suspension.
All of this comes down to positioning the upper shock mounts which I am starting to believe are The Mother of All Brackets. Here are the dimensions that I wish I knew in advance. Over the next month as I finish my upgrades, I will post actual measurements. I think a comparison of this basic information from other GT40 owners would be very interesting.
REAR SUSPENSION---------------Full Rise-----Static Ride Height------Full Drop
Ride Height------------------------------?----------------4.5"----------------?
Wheel Well Clearance------------------?-----------------?------------------?
(Top of Tire to Underside of Wheel Well)
Shock Absorber Compression---------?---------------1" 33%-------------?
(Inches & %)
Suspension Movement at Wheel Hub-?---------------+/- 0.0--------------?