After a little more sleuthing through the catacombs of the forums. I've discovered that the lighter accent color on the speaker grille, ash tray cover, and glove box door were used through early '51 production, and later '51 trucks just painted those items the main interior color. Tim Lederman had a post with a link to a GM document with the two GM color codes for the main interior color and the lighter accent color and when they were used.
LInkSo instead of masking off the ridges of my glove box door and painting just the grooves, I'm going to paint the whole center section interior color, leaving just the top and bottom areas stainless, which will match the trim on top and bottom of the speaker grille. It'll be easier, too. Anybody need some cut-to-width tape for masking the small high areas?

To be correct, 3800GUY, yours should have the lighter accent color.