First step is to determine how your valves are mesured. They are either inside diameter (easystreet/airlift valves are measured this way) or outter diameter (blitzluft).
Now that you've determined the proper valve size, go to
www.sucidedoors.com and order up your new line.
A line cutter is a good buy while your there. It will provide a clean straight cut.
Sucidedoors really for all your air ride needs. They are a company that was started by 2 brothers who built one off parts for their mini trucks and have grown to one of the best known and prefered companies out there. Still ran by guys that love building minis, and people here who know their air suspension will back me on saying go to them.
/end shameless plug