With the relocated perch and axle I would suggest you use the "trim height diagnosis" chart (steering section).So I'd be aiming for a 10 inch installed height I guess since mines is already half an inch higher with the relocated spring perch. I'm thinking the 10.6 might cause it to be a bit too high,
Motortrend reported measuring 0.83g with a stock Impala and I thought I had seen a standard circle test reporting higher.
As I have said before my target was not autocross. If my back end was high it would be just about right with a full car of people or several hundred pounds of tongue weight.
What I find weird is my LS caprice which is supposed to be stock is also showing high in pictures. This is why I suggest you measure frame to ground (front and back) to get more data points. 91SS is clear his information is not perfect and is calculated, or colored by the fact he uses air bags and is a 1991 Caprice.
As the modifications stack up comparisons to stock become more challenging.