What are the best springs that will give maybe a .75'' drop that will give me the stiffness of the stock springs. I dont want to be bouncing around, especially in vegas where the roads are horrible.

What is the difference between

Tien S Tech
Tien H Tech
Eiboch Pro Kit

 

what make year 350z do you have?
"stock feel" is different between the 2003-2004 years and the 2004.5+ years as they use different rear spring/shocks

for the drop your looking for the closest to stock spring rates would be
hotchkis for the 2003-04 make years
RSR for the 2004.5+ make years

pp