I think the 0.040" orifice supplies enough oil. But that's a very small orifice that can be easily plugged by debris. Some folks believe that's why the Ford orifices were 0.060". Not because the additional lubricant was needed, but because the larger hole is less likely to become plugged.
FYI the holes in the Moroso cam bearing restrictors are also 0.060".
I'm good with anything between 0.040" and 0.060". I'm not adamant about one particular size. Nobody has ever complained about their bushing orifices clogging up ... yet
From a lubrication and cooling stand point I don't think there's any need to go bigger than 0.040" with a solid lifter, not for street, drag racing, road racing, endurance racing. The question is, do you feel comfortable the 0.040" orifice won't clog up? If you don't, then go bigger, but don't exceed 0.060".
Bushings installed in hydraulic lifter motors should have orifices in them the same size as the orifice in the hydraulic lifter ... to ensure the lifter is not starved for oil. Oil flow should be limited "downstream" by using push rods with restrictions in the tips.
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If you use a 351C 4V powered vehicle for a grocery getter ... the eggs aren't going to make it home!