no oil on rocker's drivers side only? 360 magnum

Well guys the obvious answer is there is a blockage somewhere (or put in brand new lifters) but my problem is on my 360 magnum, there is no oil squirting out of the rocker arms on the drivers side only. I replaced the lifters already (thinking that was the problem.the lifters i put in were used which could be a issue but they are working on the passenger side. Also wouldn't it be strange that all 8 of them would not work on one side?. Is there a oil passage somewhere that oils that side of the block that could be blocked?.there is 60 psi oil cold and about 40 when warmed up. thanks for any help.