generac lp3250 model 6000. what size line(1/2" - 3/4") do I need to connect to a 120 lb tank?

The LP3250 unit is designed for use with a 20 lb. or 30 lb. tank, but can be utilized with a larger tank. To ensure the unit will properly attach to your larger LP tank, we recommend contacting a local plumber, or the propane company that supplied the tank. Generac does not offer a kit or parts to attach to any other tank, but your local plumber should be able to ensure your connections are proper and meet your local code. The regulator inlet pressure from an LP tank should be between 30 and 100 psi. Please note that any damage to the unit due to utilizing a larger tank will not be covered under warranty.