Yeah, I went back and looked at the picture of the block after I popped wise . . I'd guess that they're closer to 4" in diameter because they're actually bigger than the mains . .
Still, when you build a bigger lifter, you just create more reciprocating mass that has to change direction at high speeds and tremendous spring pressure . . so then you have to increase valve spring pressure, stronger rockers, bigger pushrods and more expensive one piece valves . . It's kind of a vicious circle . .
All the NASCAR guys are going the other way . . Little bitty cam lobes, little flat tappet lifters, skinny pushrods, and really high rocker arm ratios, 1:8/1:9 with 125# of seat pressure . . Dunno who's right, but their engines are built to go about 550 miles, while a drag racing engine spends more time being warmed than it does racing.
I guess us drag racers like kicking the tiger's ass more than tickling a mouse . . 'spose?