swapping center sections?

oh I knew id have to shorten my driveshaft. the car currently has a 7 1/4 connected to a /6. does the drive shaft need to b beefed up at all or does it just need to be shortened? how short?

The best approach is to measure it. You will want to contact whatever shop you choose to do this and ask them HOW they want you to measure it. Different shops have different methods.

When you do get to that point, make sure the car is sitting full weight on the suspension when you measure.