Chuck;
When you bore out the chambers & insert the new tubes then the chamber section has been "Sleeved", no problem there. The sleeve does not have to be full length to be a sleeve. Cutting off the bbls from the chamber area does "NOT" convert it to a "Mono" Block, anymore than it converts it to a Chopperlump, it it wasn't so built originally. Monoblocks are built from scratch, not made by cutting off a set of existing bbls.
I have noted that a lot of folks who get terribly upset over the term "Water Table" casually toss out Monoblock with no concern at all for its accurate use. Whats wrong with calling something by its Proper Name & not using the same term for Something Else.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra