Porsche Repair: porsche 911 sc, porsche club of america pca, old american cars

Question
What is general condition of 911 sc's.  They are 30 years old.  American cars would rattle etc.  Do porsches?

Answer
Two different worlds.

1) The 911 is uni-body construction vs. many 30 year old American cars which were either uni-body or body on frame; hence you would have more possibilities of rattles with "American" cars; suspension types, number of doors, etc,  also contribute to more or less rattling.

2) The typical 911 SC is driven less than your typical American car, hence less wear on the suspension and less stress on the body.

3) The typical sports car enthusiast pays more attention to his/her vehicle than the owner of something "other".

Do 1978 SC's rattle?
I think if you have driven a dozen SC's you'll find less rattle than others; in other words you might find a few that do rattle.   

Now if you single out a "sports car" out of the American group, such as the Corvette,  you might find that Corvettes rattle less than Impalas.

If you are considering purchasing an SC you can find a list of things to look for as well as current price trends.  Ross Publications Excellence magazine usually has a yearly update on pricing trends.  
Other sources of information are the Porsche Club of America (PCA) which is a national non-profit organization of Porsche owners broken down in zones or regions; this is a highly recommended group and can be reached at www.pca.org   Easy to join, lot's of great people and a fantastic source of information.   Then you have the dedicated Porsche forums such as Rennlist.org  or  Pelicanparts.com which have forums categorized by vehicle models; plenty of interesting information and  opinions.    

If you have little if any experience with a particular Porsche model you will want to consider having an experienced auto technician perform a PPI or Pre-Purchase Inspection for you. And, the easiest route to finding a "good value" is to use a dedicated Porsche "car finder" such as David Maynard at European Locators,  phone:
508.826.8614,  web http://europeanlocators.com/   who will search for, perform a PPI, negotiate on your behalf,  and deliver to your door a particular Porsche you wish for.