the early magnum blocks were drilled for rocker shaft oiling, magnum head/gasket blocked it a deck surface. in 92-93 it was either a magnum or a pre-magnum LA head no duel bolt holes on mag heads. roller lifters were the crossover.
Roller lifters predate the magnums by several years, I doubt that's the crossover.
what I mean by crossover was on lifters. the non-oil through with the solid PRs then they got a oil through roller lifter with the solid PRs. then the last of the pre-magnum roller cam engines got oil through lifters & hollow PRs oiling up the PRs & up through the heads/rocker shafts.
next change was magnum head/pedestal rockers/oil-through roller lifters & hollow PRs - LA pre-mag & magnum share same oil through roller lifter but different length hollow PRs.
which is why I said you have to watch the roller lifter you use on a magnum engine as early non oiler roller lifters do not cross over to a magnum head engine.
and when looking building a LA/magnum hybrid, I have only found the early 92-93 magnum 5.2 to have block drilled for shaft mount rocker oiling.
also why I said most 90-91 pre-magnum 318s seem to have more of a VC leak issue/PCV-oil consumption issue as they oil both ways to the rockers and that is a lot of oil in VC area splashing around.
of course this is all just my opinion from what I have found working on them.
