Adding a body lift won't help tuck the transmission up into the body. This was the OP question. The explanation is why the tummy tuck came in. Because a body lift won't tuck the transmission higher up the explanation was that a tummy tuck would. Thus him asking if a body lift would change drive shaft length required the answer that the body lift won't, but for him to achieve the desired outcome of tucking his transmission up higher into the body the required action would be a tummy tuck. And this would effect driveshaft length.