where to look for cracks

[homer41]

I may start looking for a replacement block to rebuild, where are these flathead 6s prone to cracking from freezing, are there any typical areas to look? Anything else to look at beside seeing if it will turn?  Dave

[P15-D24]

Head bolt holes, water jacket both sides, valve guide recesses. 

[dpollo]

all of the above plus through the fuel pump opening.   These blocks are not prone to crack like the competition back in the day.  The most serious, I encountered only once was alongside a valve guide.   non repairable.