www.semproducts.comI dealt with Steve Lowman at SEM. My '73 W200 crew has the green interior, and I wanted to keep it stock. The dash was in good shape, but not the glove box, and neither were the fiberglass door panels or their arm rests. As you found, SEM paint codes don't cover that for trucks. They suggested sending something in the color I wanted, so I sent the one arm rest I had with good covering and color, and they successfully matched it, at least to my eyes. It's more expensive when they have to do this, but now they have the paint as a part#, and I can order more if I need it.
I also tried their filler, to fix the ubiquitous cracked glove box lid. Could be we just suck at doing it, but it didn't really turn out that good, and I've since found another lid to replace it.
