Some great news! i got a great new job, 3x the pay.  Bad news: more freeway driving in my '74, about 800 miles a week.  Thus i am considering changing my rear gears from the current 3.70 to some freeway gears (this car is all about daily driving. the 75 handles the other needs).  As i am looking around at the Vette suppliers, i noticed that the 80-82's have some 2.72 gears, where as the lowest for pre-80 is 3.08.

  Is it possible to switch to simply put in the lower ring/pinions, or does it need some major work (differencial ect.)? thanks all!

Once you put the right gear in for the speedo correction, it should work out very well with either gear you are looking at. 

The alum case set up is different, but I would guess you could get the gear for those as well as the older style.  Either way, just be sure to have a pro set it up for you.  A mistake can be very pricy, and destroy the housing as well as the gears.

Joel and Ken;

    thanks for the tips! i totally forgot about the transmission/speedo gear, and i would have done it myself.  Its rare that i see people suggest a pro to do a job, so i will quickly take the advice.  I thought it would be a simple job, but may have just saved myself more than a few $$$. 

   Now, do i need any pro Vette mechanic, or are rear ends speciality work like transmissions?  May sound stupid, but since i didnt know to go to a pro, well....

Again I agree with Joel.  Pull it out and take the assembly to someone who not only knows how, but has the tools.  This is where you need to be carefull.  Many folks may know how, but don't have the correct tools for the Vette rear.  Granted many of them are the same.  But not all.  The aluminum carrier is a bit more touchy.