Qualified machine shop

Does anyone know a machine shop who can bore a '62 aluminum 225 slant 6? I am rebuilding the engine and need to bore it 30 thousandths. I have been to several reputable shops and they all say it will require some type of reinforcing plate to secure the sleeves to the deck while they are being bored. Seems the sleeves "shimmy" when they try to bore it without the plate.

i would not go that much...