I know your probably looking for an original piece, but if necessary I'm pretty sure I bought this kit just for the tee connector from Ames for mine. Need to check my receipts. Ames Part # N175W
Todd makes a kit too. I kinda pieced one together using a similar tee. But you know how I am! It gotta be a GM piece!
I have these that are originals . . . Not sure if these are the ones you're looking for? I didn't clean them up at all but a quick "low pressure" bead blast would have them looking like new.
Those tees are correct for the one that splits to the manifold vacuum fitting on the carb, but the tee he is looking for is up under the ram air assembly. It has all 3 outlets the same size.
This plastic T is very small, about the size of a dime. Like Adam said, it goes up under the snorkel. There is not a picture of it in the assembly manual because I believe the entire air cleaner was built as a sub-assembly. The metal T is pictured in the vacuum hose routing page as shown below.
