Where there are duplicate threads and there are votes for both, the threads are merged and, typically, the earliest one becomes the sole thread for that car - the only time this doesn't happen is when the earlier thread is rubbish and I'll assign it to whomever made the best effort instead. When the merge occurs, the votes are merged too so that no votes are lost.
When I eventually get to "M" - which will be a while since I keep being pestered about other threads and perpetually having to explain things rather than getting on with the job of sorting it out - I will judge whether there are duplicate threads for this car and, if there are, merge them.
Speaking of merging posts, if you could STOP DOUBLE-POSTING, that'd be great.