Here is a pic of my 73. The tail panel on your 74 was painted the same way.

The black areas around each tail light are "organisol". It's a slightly textured paint.

The housings themselves as well as the tail panel are painted with textured argent. There isn't a correct color on the market right now. Your best bet is to mix and match shades to get something close.

The dark argent is too dark and the light argent is way too light. What does work good is to spray the dark argent as a base. When the base is still wet, lightly spray the light argent onto it. You end up with a color that is darker than the light argent but lighter than the dark argent. There is a member here "joelson6" that did this to his car. It looks really good.

Totally Auto sells textured argent in spray cans. Krylon also has textured paint in their "Fusion" line that I've heard is a really close match.

Also, the factory sprayed the argent up underneith where the truck lip sits about an inch. This was so that no body color would be seen between the trunk lip and the tail panel. I've seen some people stop the argent right at the bend in the tailpanel which isn't right. It goes around the top bend about an inch.