In Orange bowl.
One reason Miami jumped all the way from 5 is because there was no other team that stood out as a clear cut number 1, since they beat the team that was number one, voters moved them up, even though it took Tom Osborne deciding to go for 2 and the win with 1 second to play to beat Nebraska.
An undefeated BYU would have had its claim on the National Championship, and could have gotten it if they were 2-4 before the bowls.
This link explains a little more about 1983 and how the top teams compared, scroll down to number 6.
http://bluecougarfootball.blogspot.com/2010/07/defending-1984-national-championship.html?m=0