Regarding converting 59 engine block to 1960 engine "conventional" cooling style block, see
https://pontiacsafari.com/EngineCooling/index.htm and scroll down to the heading "
Engine Differences in Reverse Flow and Conventional Flow"
The 59 engine with reverse cooling first distributes cooling water evenly front to back in each head through the water distributing tubes. Water then flows from heads into the block evenly from front to back through holes in the deck.
The 60 block first sends cooling water directly into the engine block and then up into the heads with more water directed to the back of block and heads. Water flows through the heads towards the front then into the intake manifold and from there into the top of radiator.
To accommodate the difference in water flow and cause most cooling water to flow to back of block, the 60 block has fewer and smaller water holes in the front of deck than the 59 deck. So to convert a 59 reverse flow block to a 60 conventional flow block, you would need to close water passages in the deck towards the front, and I maybe reduce size of some passages.
You would also need to use a 60 front cover and add a water hose from intake manifold water to the front cover.
Does that cover everything? I'm not certain but I think so. I once considered converting a 60 block to 59 reverse flow style but decided against it. Thus the article I wrote to attempt explaining the differences in reverse vs conventional flow blocks.