S130 Spring Rates and dimensions

[Perandor]

I'll start off by stating, I have searched (quite profusely) and have not found a definitive answer.  I'd like some advice before I go out spending money.  The patient is a '79 280zx. 

 

While I could wait and save the $1400 more or less for coilovers, I have decided on Koni Adjustables from thezstore.com and springs.  Although not the usual suspects because I want to try something new.

Questions:

1. What spring rates to choose for a street only (no plans on racing it)?  I've read 150 front/ 175 rear as well as 175 front/ 200 rear as common factors in slight performance upgrades while still offering a comfortable daily driver experience. 

2. What OD spring do I need to choose for the replacement springs?  I've checked out the Eibach kit and the Vogtlands, but didn't see this as published data in the product descriptions.  (example, 5"?)

3.  What considerations do I need to remember when buying shock components?  Noted, this is what I have on my list to buy: bump stops, springs, Koni struts. 
4.  I assume 11" free length will be alright?  John C on classiczcars.com suggested 10" tall (coilover) springs at a minimum for the spring rate range I'm interested in.  - https://www.classiczcars.com/forums/topic/33587-struts-and-springs-buying-guide/

Stock Spring dimensions/ data:

Front diameter
150mm/5.91"

Front free length
311mm/12.24" (coupe)
320mm/12.6" (2+2)

spring rate: 2.26kg/mm or 126.6lb/in

Rear diameter
100mm/3.94"

Rear Free length
353.5mm/13.92" (also listed for GS130)
361.5mm/14.23" (this is a second listing, says it's for a S130J)

spring rate: 2.51kg/mm or 140.6lb/in (coupe)
2.67kg/mm or 149.5 (2+2)