its a 727, right?

quickquestion to verify. my uncle has an all orignal 73 charger w/ a 400 4 barrel w/ an automatic. hes the 2nd owner, but has had it since 73. anyway, with the 400 BB, he must have a 727 not a 904, correct? just double checking. and he would have an 8 3/4 rear as well? what kinda of gear ratio would he expect to have?

thanks