Magnum block mdded to oil LA heads?

I think if it were me, I would either do what YR said - use the OP sender passage and bulkhead fittings like the Indy spray bar setup. You would probably need some sort of restrictor in each line to the heads. Or I'd get an LA block. It's less of a risk than drilling, and drilling still leaves the factory "timed" delivery unless you groove the cam, and then you're married to that cam assuming the shop doesn't miss a 1/4" target while drilling through 6" of iron.