Not sure where you get your stats for weight but my base 5.0 coupe is right at 3500, cobra base coupe is 3650 and up. This cobra was also a vert, which adds a little more weight.
Every time I have seen curb weight numbers for 5.0s they were over 3600lbs. But whether they were fully loaded or base, I don't know. Nor do I know what the difference in weight between the two are. You at 3500 lbs and him being a vert he would still have a power to weight advantage over you.