I have the original 3 inch driveshaft and a 3.5 from a caprice classic. My 68 will have a 700r4 and magnaflow exhaust kit. driveshaft has to be shortened anyway. Which would you use? Would 3.5 be too large?

I have the original 3 inch driveshaft and a 3.5 from a caprice classic. My 68 will have a 700r4 and magnaflow exhaust kit. driveshaft has to be shortened anyway. Which would you use? Would 3.5 be too large?

Horsepower and drive shaft speed are important considerations when choosing a drive shaft. A first gen Camaro drive shaft is close to 50" depending on transmission choice. I would go with the 3-1/2" if it will fit with no obstruction. The extra 1/2" diameter raises the critical speed capability and also makes the shaft a little stronger. If you are using a 4.10 or higher rear end, drive shaft speed can be very high at higher road speeds.