Need a new set of springs for my 76 z. I bought some used (stock)ones from a junk yard, and now they are wearing out.

I need a new Set that would only slightly lower my car and will still be a smooth ride

Honestly, do a search on the forum here and on zcar.com. There is a lot of information to be found. I am not saying this to be mean. The number of threads you'll find will far exceed the number of responses you'll get.

To start you off, there are a few options available to you (and use the names are keywords in your searches): MSA, Arizona Zcar, Tokico, and ST (don't think Eibach makes the 260 springs anymore).

You can get a set of Tokico HP springs AND shocks off of ebay (JDMwerks is the seller) for $389 shipped. I just picked some of these up for my 240 after much research and deliberation.

http://www.classiczcars.com/forums/showthread.php?t=20120

Lot's of info in this thread and the thread starter also had a 280z. I suggest a progressive rate spring with a softer strut (kyb?) to achieve what you're looking for. Personnaly I have the Eibach's with Tokico HP's and I love it! Probably a little more firm than what you're looking for. That Tokico setup that KTM mentioned is a good deal, so it's something to consider.