Thank you everyone for your opinion. First of all this shop called Dans Driveline here in Las Vegas would be the best in town as far as for honesty and the work they do. I have had work done there before and I have a few friends who think the same as I do. They are the best in town, not cheap but I want it done right. I don't want to change my trans and I really don't want to work on the motor except for maybe a different carb and intake setup. It already has a Edelbrock intake and 600cfm carb along with a mild cam. I didn't build the motor myself on this one so I don't know the cam size.Heads are stock. What I do know is that five out of the six u- joints are stock. So, they and all the rubber in the back are getting brand new stuff. As far as the spider gears, they are just old. And YES, I know thats not common for those to break but there is a broken one. This rear is all stock and I will be replacing the cover for sure. And Yes, its hard to find the gears I want, but its not the end of the world. I would like 410's but they would have to build me that and they can't get the gears right now. So either I get what I have now completely rebuilt or go with the 390.Or, go with the 430 which includes the third member of course. I don't drive the car on the highway, just local streets. But I think the 430 might be a little to much as far as the 3750 RPM at 60MPH . But my question to you guys is simple. Has anyone here gone from the stock 370 to the 390? And if so, did you notice any difference off the line compared to the 370? And if so, how much of a difference? Thank you all for your input.

 

Rookie here....Im guesssing you would need +0.4 gear increase to actually feel the difference in a noticeable way off the line.

 

If your Drag raceing you may notice a small change in 60ft times. If not raceing, you'll never notice a thing in your "Butt-Dyno".

 

You just asked the same question in the link below, why start it again?

https://www.corvetteforum.com/forums...post1603806529

 

Assuming You have 27" tall Tires on it now find some 26" or less and drive it around the block. and You will have your answer.

 

You have three threads on this very subject. The answer is still the same. An increase from 3.7 to 3.9 is a difference of less than one percent. It is not significant. There are too many variables that greatly enhance your launches, a big one being your reaction time.

But we are talking about a street car, Aren’t We?