Resurrection of a thread :):) 

Why, coitainly....all ya gotta do is change the cluster gear, and the 1st, 2nd, and 3rd gears on the mainshaft....or just swap the trans for a wide ratio and be done with it.

As far as NCRS stuff on the gear ratios, it wouldn't matter at all unless you were going for a P/V(performance verification). They check the rpm vs speed, and mileage on that, so you wouldn't be able to get away with a rear ratio change.

I have decided not to change the rear end, mostly to keep the car in its original configuration.  I just learned the it has the "Rockcrusher" transmission, so I am going to keep that too.  Had the U-joints replaced; the rear strut rods and the 4 shocks.  Also, had the inside rear wheel bearings  lubricated with a device that I got from Zip Corvette.  I am just going to live with the 3.70 rear end, since the car really runs great with the setup that the Chevy engineers thought was a good compromise at the time.  The car is a "trip" to drive, but it is just my toy, since I have a 2011 Grand Sport as my daily driver.

Sorry but a move to a 3:53 rear is not worth it.  If you want to get your gas mileage up say, above 20 MPG, you will need to go to a Tremec 5-Speed trans and a 3:07 rear.  We have tried every variety above that (ie 3:36, 3:55)  and you struggle to get to 20 MPG.  I, too, have a '77 and all that numbers matching stuff is nice but doesn't really move the $ needle.  I would make the changes that improve driveability and save the original parts.  Gas was under $1/gallon when these Vettes were new and the big gears helped with the smogged engine performance.  I have a Turbo 400 automatic, L82 with a 3:55 rear and it races at 70 MPH.  I'm going to a 2:87 rear with an engine rebuild over this winter.  Only has 61,000 miles but valve seals and guides are leaking.

hi  I know on this site the fellas  don't like overdrives  I have used overdrive in my 49 ford to 73 chevy p/u  easy to do  takes up no room   little bit      nobody likes them.my 79 runs 3200 rpms at 60 mph hour  50 to 60 miles cost a half of tank of fuel,i have looked high and low  for a overdrive unit   no luck   contact a company that's sales overdrive  they want me to buy a new 5 speed   at 5,000 $  not going to happen,going to calf  this mouth  I will find a overdrive unit if I do  I will tell you  and you can do as you wish  good luck  dwa     p/s  can stand using that mush gas for short trip.