just use a 70mm italian spindle. you don't need to match up the spindle to cups . . . i asked myself the same question a few years ago. i have a 1954ish holdsworth la quelda that for some reason a 68mm spindle does not work in. i tried, out of curiousity, a 70mm spindle and it worked perfectly. still running it a few years later with no problems.
also, absolutely you cannot make italian threaded cups work in an english threaded BB.
and don't worry, i haven't forgotten about that TA chainring. as soon as i get back from visiting my folks i'll check the teeth count and send you a picture.
also, i have never seen a 73mm italian shell in my life.