My take on the oiling system crossover tube for the small block

Marcohotrod said

the large chamfer leak problem depends on type of lifter and amount of cam lift, may be a problem, maybe not

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The type of leakage that you are talking about is the type where the oil band may uncover the large oil feed passage in the lifter bore and drop the main oil pressure. This would as you say vary with the type or design of the lifter. That is not what I am talking about.
Those blocks with the large chamfer even with a stock lifter have less precision surface contact because the large chamfer has machined it away. This leaves less surface contact and allows the oil to leak by easier. IMHO those blocks leak more.
Pittsburgh racer has mentioned in another thread that he would never build another small block without tubing the block because he had oil pressure problems from all the leakage around the lifter bores.
This was with a flat tappet cam. He said the lifter nearest the back of the block were leaking the most. To figure out why it was low on oil pressure he pulled the intake while pre oiling the motor and said he could not believe the amount of oil leaking around the bore.
Those big chamfer blocks are even worse for that. IMHO