Scot,
The 3.8 E-Type flywheel is scooped right out on the front side and is much lighter than the 4.2 version. The extra machining will be seen if the inspection cover is removed from the front of the bell housing.
The engine number will also be stamped on the periphery of the flywheel and can probably be seen though the timing hole in the top of the bell housing.
Here’s a 3.8 E-Type flywheel on the right beside a regular 3.8 item
