All you need is in the links I posted above. See:
http://www.zf.com/corporate/en_de/pr...sp?newsId=3885
Which is from ZF's own website, clearly names the 8HP50 and 8HP75 (third paragraph) and explains that they are the 2nd gen version of the 45 and 70. Also:
https://en.wikipedia.org/wiki/ZF_8HP_transmission
Which does the same but being wiki isn't as authoritative obviously and no I didn't write the page.