Andy,
There are alot of small indicators to tell the difference in the various versions of the FE, but only one sure way - Measure the bore and stroke.
If the bore is 4 1/4" (4.232 to be exact), it is a 427
If the bore is 4 1/8" (4.132), it probably is a 428 or could be 406.
But be cautious, some smaller FE Blocks could be unscrupously modified to get to this bore. The smaller FE's have a 4 1/16" (4.050) bore. You'll read other threads about guys buying what they were told was a 427, only to learn it was a modified 360!!
Once you know the cube's, the finer details will help you establish originality.
Regarding the heritage of a given motor, they were not "serialized" so it is very difficult to tie to a given vehicle.
Something to start you verification: If the sides of the blocks around the
oil pans and motor mounts are IDENTICAL, be suspicious. The 427 has sidebolt main caps, the original 428 does not.
Paul
Lot's of clues but only 1 sure way
Threaded Mode
