I would check the cylinder walls before going much over 3 3/16 on a 3 1/16 block...at 3 3/16 +040 you usually start getting real thin walls on good blocks...
Ronnie, he stated in a post above that its a 59 block but its the odd "replacement" block with a 3 1/16 bore.
I have one of these stupid blocks, and I'm very surprised it went 3 5/16 without windows in the cylinder bore.
Martin.