I need to obtain a set of lobro joint sierra driveshafts for an upcoming diff change.

I will be using a 7" diff.

Are there different lenghts out there, and if so which ones do I need?

AFAIK they're all the same length.

HTH,
James

Thanks James, do you know if that includes the cossy?

does this also apply to the push-in shafts? (obviously number of splines is one thing to bear in mind).