I think maybe its a reference to the new Boss351 block
http://www.autoblog.com/2009/06/13/f...-engine-block/
available in 9.2 & 9.5 deck height
from the article...
"
Max stroke is up to 4.25" depending on crankshaft manufacturer with max bore size topping out at 4.125" with coolant cross drilling. A non cross-drilled block with increased bore capacity will be available by 3rd quarter."
guessing this would get you a 4.00 x 4.125 in a 9.2in block (?)
LoBelly