Factory hydraulic roller set up on an older block?
I did a mockup of this very thing for my 67 318. The oem roller lifters are too tall and the oil band cleared the top of the lifter bore with just the stock 318 cam. If you wanted to bush the lifter bores, i’m sure that would correct that problem. But after all that hassle, it would probably be cheaper to just buy the retro fit lifters and be done with it. I’m just going with Morel’s and probably solids to just be done with it