I have a test engine (1941 235) that I did just what you are talking about for an experiment.
There is no way for oil to enter the lifters from the top from 1953 on, so I vented the lifters on the top so oil could enter.
I have only run this engine on a test stand, but it works fine there.
In my
blog post on hydraulic lifters I show venting lifters to allow air to escape, but the same thing can be done to allow oil to enter from the top.
They make sealed, oil filled lifters for airplanes, that is what got me experimenting with 235 lifters.
This idea would allow you to put hydraulic lifters in any Chev six back to 1929. That is when Chev started using this diameter lifter.
I have never heard of any one else ever doing this, so if you do, I would love to hear the results.
