Find the drill size for the thread tap, that will be the inside measurement for first sleeve. Second will be the tap size, ideal would be both pipes the same outside measurement or better yet small one fit in the big one, only would need one of each, then drill out intake for the larger one to fit. A machine shop could make both real quick, make up both about 12” to replace for wear. A heavy weight on top will hold it down to get first one made or long threaded rod thru intake and empty block, plate on top and on bottom of block holding the rod.