Every one I have seen from early '90s to early 2000s have had both sets of mounts, although I have never seen a factory application that used the LA style mounts- they have all used the mid-block mounts. The only reasoning that occurs to me is that with the early Magnums (where the blocks were still being drilled for rocker oiling) they may have wanted a "universal" replacement/warrantee block... and never bothered changing the tooling after that. Pure speculation on my part, never saw any published reasoning behind it.