The Stovebolt Site Forums The Shop Area Engine Shop oil galley confusion

If engines could talk, I'd like to ask mine what the heck did the previous re-builder/s do to you!?

I'm not sure anymore if it is a '56 block or a post 58 block?

It appears to have a '56 date code, but the oil passages are that of a post '58. (picture attached [img]https://imgur.com/8tkfNO1[/img])

There is also a threaded plug near the cam journal where one could fit a '56 style oil supply tube.

Did somebody miraculously drill out a '56 block to have newer oil plumbing?

The other weird thing is that the oil passage looks intentionally plugged with lead up on the deck. It was using a drilled head bolt instead.
The rockers were post '59 style with the offset groove... I thought the drilled bolt was only supposed to be used with older center-groove rockers? Although, it seemed to work fine as it was.

References:
Post '58
pre '58
hole-bolt

Engine forensics...