Cant make this valve train noise go away!

You all have brought up interesting points. On my 360 it is a junkyard pull I bought for 200 dollars and when I changed the intake, oil pan, and valve covers it appears that I was the first to open it up since 1974. Mine only makes the rattle/knock at cruising speed on the freeway with light throttle. Whats funny is it makes the same sound in the driveway when brought to that rpm range in neural wheather warm or cold engine. Mine sounds alot like a rod knock but carries good oil psi. I did notice some wear on the lobes when I changed the intake and the miles are unknown.