vacuum hose size for 83 300sd

[VaBob]

Howdy all, first post here. Just bought a high milage 83 300sd in decent shape to tinker with and keep miles off the other car.

Bought it knowing it shifted hard, and took a peak at the vacuum hoses. The line to the transmission had been temporarily fixed with a rubber hose slipped over the hard hose. Well age and nature killed the rubber, and finished off the pvc hose, or what ever its actually made of. I have access to pvc and hi temp poly tubing but I can find what size I need form searching the forums. Can someone help me out with that?

thanks