...a few things to add.
First,
Heat CAN BE your friend, but just don't get the cylinder too hot. 450 is pretty warm. You can easily anneal the cylinder by getting it too hot and letting it cool too slow.
Second,
The sleeve will need to be "seated" after it cools. It is no secret that when the cylinder is hot, it slightly expands or "grows" in size. The sleeve is cold, or better yet at room temperature. Well when the sleeve is dropped in, it rapidly heats up to the cylinder temperature, hense it grows as well. Well now as the parts cool, they shrink. The sleeve will not be sitting exactly on the counterbore step anymore.
Well this is all well and good until the cylinder head gets bolted down adding tons of pressure to the sleeves, or the motor detonates a few times, or the jetting gets a little lean and the motor gets nice and toasty.
Then the sleeves drop just slightly to sit on the c-bore step. Blown head gasket or o-ring.
Third,
I can't imagine the sleeve sitting exactly at the level of the cylinder deck, so it will be slightly sticking up or down in the hole, so it will need to be decked and bored anyway.
Brian