Wiring radio, Constant power lead?

[Rc 415]

I'm trying to install an Alpine deck into my 83 c10.

The only wires that are behind my dash for the radio are the gray, black, and yellow. Right now i have the battery lead and constant lead from the radio both connected to the yellow wire in the dash, and the ground connected to the ground. I do not have the gray wire connected. The problem is, I cant save presets and the time, because every time I turn the truck off they get reset due to the constant wire not being connected right. What am I supposed to have the constant wire connected to?