In the worst case, if you don't want to change anything, you can still slow down the BPM a bit, like -1 or -2. It won't be hearable, won't ruin the song quality (unless if you're slowing it down slightly) and will make your map a bit longer, to reach 5:00.
You'll indeed have to replace every single element and timing point in your map, but it's still a solution if you're not lazy or don't want to change your mapping.
In all cases, you'll have to reach 5:00 in order to rank it, because that's how the RC are, and there's still no marathon map ranked below 5:00 since 2007.
(except if the QAT decides to make an exception)
Good luck!