The fastest ones i've typically grown are gifts from some of my american amigos in a private cultivation club (I think they're called the Groovy Gang, but may have got that from only fools and horses)
Stone99V6 was one of the fastest, but lots of S1s with hybrid vigor seem to not go past 65 days (55 was my fasted i think)
I've not grown much in nearly a year so maybe
@Frankthetank might know some commercially available ones - also i think Sawney Bean does a lot of cross breeding so perhaps he's also got some fast strains he could reccomend.
I've gone with the ole fashioned DP white widow this round - i'm guessing its closer to a 70-80 days turn around