We have had the 65-67 Metal Floor Pan Drain Hole Covers for the Mustang available for quite some time. They are technically correct for just the 65-67 Mustangs, but most owners always used them for any year from 1965 to 1973. They will fit and function perfectly in any of those models.
We now have the correct ones though. The 68-70 Drain plugs are shaped differently from the 65-67 ones. Now they are available as part number SM-1112.
1968 Mustangs use 4 per car. 1969-70 Mustangs use 2 per car, and vehicles equipped with staggered shocks require an addition 1 for the trunk reinforcement. 1971-73 Mustangs use 2. (Please note that these covers are not the 100% correct shape for 1971-73 model years, but they are very close.)