Ideal location for 14"x12" hole in basement wall

I'm trying to determine the ideal location for a Takagi direct vent wall terminator. The rectangular hole will need to be about 13-3/4"x12" in the 6' wall constructed of 8" block. I'm wondering where I should locate the hole for greatest structural integrity. Where should the hole be relative to the grout joints? Will I need to reinforce the hole somehow?

Provided you have no point load above the hole, it shouldn't matter much where it is.