[Buzz]

My opinion is that it's absolutely pointless when the two major components of the car - body and chassis - deviate significantly from the original construction. Before someone assessing the "correctness" of such a car by looking that closely at the drivetrain, they would notice the fiberglass body. If you were talking about an aluminum bodied car with a full round tube frame that you wanted to make a project of closely replicating an original, then yes, extra attention to those details would add value towards that goal.
ERA does a masterful job of creating a visually correct replica that has almost everything right in terms of shape, stance and most other visual details, so if it was me, I would focus on just that - making/keeping the car looking "right". I really do not see what value things like correct date coded and casting-marked drivetrain components and authentic jacks and grease guns add to a 'glass bodied car. In fact I don't even get it from a bragging rights perspective.
In most cases it would go like this:
Owner declares: "It's got a 1963 289 HIPO Block and Heads, with 5 Bolt narrow bolt pattern Bellhousing and 4 Speed T10 B/W Tranny ALL WITH correct 1963 and 1964 Casting Marks!"
Pleb replies: "Body's fiberglass, so it's a kit car, right?"

In the event, however, that you are doing this for your own personal satisfaction and not to make an impression on anyone else or to increase the monetary worth of your replica, then by all means absolutely go for it. After all - it's your hobby and your project. Come resale time, you may even be lucky enough to find a buyer who values these details as much as you do, and having them on the car will indeed be a plus.