ol' slant is dead... need help!

Thank you very much redfish and memike I definitely will start there. The knock was only a little tick back when I would drive it for about 20 minutes at freeway speed (65) I've been asked a few times about the hydraulic lifters but I wouldn't know. I do have a oil light but I didn't think anything was going on since it would come on when my motor was warm and the idle stayed the same. The light would only come on at 1000 rpms. I will definitely start with an oil change. What does it mean if my oil DID smell like gas? Oh and its a 75 slant 6 225.