Did you try screwing it in with no gasket? I have seen where rebuilders use too thick of a gasket on them and it pulls it too far away from the lever. If you don't hear a physical snap or "clack" sound when you push the reverse lever into reverse there may be an internal problem.
Gus
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60