"Numerically," I definitely see comparison to '80 (especially with having at OSU as regular season conclusion).
I might lean a little more toward it being like 1981. Started 5-1-1. Tied OU — not a great OU team, and probably should have won, but was considered "big deal" at the time. Beat Iowa at home (UI ended up Rose Bowl that season, ugh). Defeated Missouri (ranked at time of game). Lost four straight down the stretch, including one to KSU (finished 2-9).
But we're doing cart-before-horse, of course, of course, to presume 5-0 is going to turn worst-case second half this season. It's easy to start thinking "we've seen something like this a few times previously."