they don't know squat . . . .
tail shaft is a tail shaft if for the correct tranny . . .
and a correct built 700r4 with info on the end use it will get you a unit that will hold just fine.
call this guy up greg . he is over on ck5.com a lot and gives super help and info on tranny questions. he has built a few for members and shipped them . I have done parts deals with him and super stand up guy .
http://www.phoenixtrans.com/