No need to shorten the driveshaft.
You may need to change where it attaches to the axle flange though, the 8.8" has a larger flange than the original 7.5" axle.
Some people simply redrill the larger flange for the smaller driveshaft bolt pattern, though I would suggest changing the driveshaft to a u-joint style if that's not what you have now (the original dual-CV style driveshaft is not known to be reliable).