Holy crap, you just sent me down a Google rabbit hole. If you search for "how tall is jim jordan" you get various results saying anywhere from 6'0" to 5'8". But the author of this
Twitter thread seems to have done some sleuthing, and for one thing, he wrestled at 134 in college. Not a lot of 6-footers who are that skinny (much less competitive wrestlers).
Also, if you just look at a bunch of
pictures of him standing next to people it's very clear he's on the shorter side
(the photo of him with Matt Gaetz is particularly revealing).
My educated guess would be 5'6", max 5'8".
By the way, if he does pick Jordan we should all agree to drop the "Gym Jordan" jokes (which I've always found to be offensive) and just make fun of his height non-stop, since that will be the quickest way to get Trump to sour on him.