60 lbs in one harvest is quite a bit for indoor growing. I think the best way to do it would be to have hydro SOG with 200 plants every two weeks, averaging a yeild of at least an OZ of each plant. In 2.5 months of flowering you COULD POTENTIALLY have 62.5 lbs...............in theory. I hope you have you shit together. That's a hefty indoor op you're talking about there, and it's the type of thing you're only going to pull off for so long (assuming you don't get caught right away) before you get caught if you're planning on doing this in a apt or house in a residential area. It would require a space where large amount of electricity get used on a regular basis so it wouldn't seem abnormal.
Or, you could try to do it all at once. Good luck with that. You'll need a small warehouse.