ever read the story about the guy who sold his livestock farm to go diamond hunting?
the lady that bought the livestock farm found the worlds largest diamond one day while gardening.

I would have the 340 block sonic checked first and foremost before you go do anything. it might just check out better than any of the 360 you end up with.
cost after that to do what you want would be the same.
a stock bore 340 is 4.04" bore . 3.31" stroke (exact same as 318)
stock 360 is 4.00" and crank is 3.58" the crank journals on a 360 block are different so cranks wont swap..(common knowledge)
but to bore a 360 to 4.04 you have to remove material...and most likely end up with a thinner cyl wall..
Sonic check the 340 first..if its not good on the majors..then look for the 360..
but in any case i would source the best bore thickness block in the equation..

just my