Get a custom torque converter made; we know that works. AFAIK, nobody's ever tried turning down the snout on the later-type torque converter, so we don't know if there's enough metal to do so without spoiling the converter -- the people suggesting it here are guessing without knowing if it will work. if you're up for doing that experiment and taking the gamble that you'll have to buy a new converter anyhow (immediately when the machining operation breaks through metal or later when the too-thin remaining metal breaks in service) then go for that, but if you're not a gambling man, do it the way that is known to work.
