You can actually redshirt in any division. All you need to do is not compete. You can only redshirt one year that you are enrolled in school full time barring some special issues where you could get a hardship redshirt.
If you take online classes and are under 12 credit hours per semester you actually will still be able redshirt a different year because you are not enrolled in school full time.
I am from a similar background. Most of my prs in high school were very slow (5:07, 11:45, 19:07) but had really gotten hooked towards the end of my high school career. I went to a division one school my first year that would not let me walk on but I ran with the club team the whole year and made large jumps in my running. I transferred to a division two school after that and worked my butt off. I ended up getting my college prs down to 3:56.66 in the 1500, 15:32 in the 5k, and 26:01 in xc. I won our conference in the 1500 and got all conference in cross. It was a lot of fun and has really been a large portion of my life.
I personally would look at division 2/3 or NAIA schools that are quality programs and allow a lot of walk-ons
I am from Indiana and some schools that come to mind are USI and Wabash or the school I went to University of Indianapolis (I loved it there). I have heard numerous stories of guys that were jv high school runners that got a passion and took off in college.
If you really want to be good, go to a good school that will really develop you and WORK. I don't know you, but I bet you still can get a TON Better! Also make sure it fits you well socially and academically. Make sure the school fits you in all aspects or you wont enjoy it.
Hope this helps.
Mike Landy