1969 Race Dart w/ 426 Hemi- garaged for 45+ years

Would be interesting to take a closer look at the MC adapter plate.
Looks a bit different in size and form? More 6" rather than 5 3/4" ?
And again, thanks for you sharing all this.
View attachment 1716092922
I have pulled the MC, does it matter for the size of the plate replacing the new one? I have the same MC as a replacement.