Hi Classical Glass,
You can't identify a side oiler by casting numbers. FE casting numbers were all over the map.
Take a look at the link posted by shootnride.
Here it is again:
427 Block Identification
The pic (in the link) by blykins shows the timing cover area and a plug where the side oiling passage was drilled. There's a little red arrow in the pic to highlight the passage.
The pic posted by dcdoug shows 3 cross bolts - near the blue paint. Immediately below the cross bolts (block in pic is upside down), you'll see 3 small allen plugs. These plugs are for the side oiler passages. You'll also see a hump in the block to make room for the
oil passages.
The pic also shows screw in core plugs. Early 427 blocks had normal cup plugs, but I believe all side oilers had screw in plugs.
Will.