The venturi is part of the upper body, and is not removable. You can use the procedure published in the January February 1977 issue of the Restorer magazine to eliminate the warp in a tillotson carburetor.
Remove all gaskets and reassemble the two halves using the bolts to hold the top and bowl together. Use adjustable hose clamps to bring the two halves together slowly and carefully. See attached photo. Put the carburetor in the oven and turn the heat up to 350-400. Heat for three hours. Remove the carburetor (it's hot!) and allow to air cool. Reassemble