yes, I'm using RG, But i doubt i can answer any of your questions.
RG makes absorbers only, and they have other ppl make the springs for them. (IF i remember correctly)
THe mounting brackets should be able to fit in springs from other makes such as HWL (which i am wanting to try out soon)
however, the springrate they recommend you would be a good guideline to start with.
remember to inform the guy who service ur shocks of the springs u r using. just to let him match the shock rate (but i dunno does he really match them correctly anot coz i havent revalve yet)
u just have to drive the car and feel it with YOUR own ass to see if you like it anot. an absorber and spring is just like .....a spring and an absorber :lol:
contact Mr Jack from RG, I believe he can arrange a suitable set to your liking.
his contact can be found below.
http://zerotohundred.com/forums/index.php?showtopic=42248
p.s: do a search be u start a topic ya? ;)