ok this is probably a silly question, but here goes

is driveshaft length same with 10 and 12 bolt rears?

sorry for newbie/silly question, thanks for answers

i need to know this as well switching from a 68 10 bolt to a 69 12 bolt soon!! in my 68 4 speed sb camaro

Yes, they are!....The only difference are the size of the U-joints!