Seems like the max recommended by everyone is 0.030", no matter the application. Us old guys are used to the thick walls of older blocks and you could bore them 0.060" with no problem. Nowadays with the thin wall casting technology used by the factories and instances of core shift, it's just not safe to do. Smokey Yunick said you need a minimum of 0.130" cylinder wall thickness all around, so if you sonic check the block and figure 0.130" wall will be left after boring and honing to size, go for it. Your walls would have to beep to 0.140" all around to qualify.

Heck, we used to bore the old Merc flatheads 0.187"-over to make 286 cubic inches.