Many, many years ago I was living in Southeast Georgia (Coastal Plains) and tried to prepare for a multiple day Gaps ride in the best way I possibly could. Our industrial park had a railroad overpass that was much steeper and considerably longer than any climb in the area so I did repeats on the overpass and eventually built up to doing them in the biggest gear/fastest pace I possibly could. I want say I did great in the Gaps, but I managed pretty well. Of course I was much, much younger at that time. There is no replacement for actually climbing steep grades, but sometimes your options are limited and you just gotta do what you can.