8 1/4 to 8 3/4 driveshaft changes

No their not the same length but there's not a big diff. Maybe like 3/4" difference. If you had to pull it out 3" too get it in place it's way too short and you need a longer driveshaft. You should only be able to pull it out approx. 3/4"~1" max. With it too short it may work for a while if it's a low power application but it may also vibrate and eventually will fail.