272 and 292 are not the same castings but use the same crank and main journal size.
292 and 312 use the same casting but 312 has a different crank and main journal size.
312 cranks can be machined to fit 292 blocks
Y blocks vary in cylinder wall thickness because of core shift. Checking the thickness when rebuilding is by far the best way to determine how far you can bore.
You'll find that John Mumert and Ted Eaton are amongst the best sources for Y block parts, information and machining. They are both members of this forum.
cheers
Warren
Grizzly (Aussie Mainline)