442 W-30 Documentation

[Scrooge]

Hello, all:

I am currently looking at a '70 442 W-30. The car is represented to be numbers-matching, but the seller has no protect-o-plate or build sheet. All of the W-30 specific equipment looks legit from the pics I've seen so far.

I am not very familiar with GM cars as I've only dealt with (and owned) Mopars. My questions are essentially as follows:

1. How important is the protect-o-plate in terms of authentication and valuation?
2. What is this item and is it different than a build sheet?
3. Do you know of any registries where I might verify this particular car's VIN as an authentic W-30?

Like I said, I am new to these cars and simply don't want to get burned. Thanks in advance for your help!

Matt
'70 'Cuda 440-6