Thanks for the response!
I actually feel pretty good on the bike right now, and I’m confident I could complete a century if it were this weekend, the trouble is maintaining and ideally improving my fitness throughout the miserable Minnesota winter that has just begun 
I did notice that the longest ride in either plan is around 2 hours. Would there be any benefit to extending or swapping out any of the rides for longer 3-5 hour sessions as I get closer to the event? (I say that now like it’s a walk in the park to sit on an indoor trainer for 5 hours)
Thanks again for the help!