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If by "block mod" you mean smoothing out the hard 90 degree turn the oil makes right after entering the block, I would say definitely do that. It is a 10 minute deal and costs nothing if you already have the tools.
I don't think increasing the oil pickup to 1/2 is necessary, but it does not do any harm unless the procedure is messed up. At that point it does a whole bunch of harm  I would never do it to one that looked thin to begin with. So if there are any second thoughts, don't do it 
1) Smooth the turn/intersection
2) Using a milling machine to do the 1/2 NPT is safer/better than by hand. It allows moving the centerline ~0.050" to keep more meat on the boss.
3) You can use a pickup with the 3/8 NPT thread welded to a larger tube for some of the 1/2 NPT benefit without enlarging the block boss.
FWIW, all my big blocks have the 1/2 NPT mod and the enlarged oil passages to the mains.
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