[vettestr]

Sleeves installed in a cast iron block need to have steps or a shelf cut in bottom of bore to seal and stop the sleeve that is an interferance fit or pressed into the block. This is what retains the sleeve in the block plus the fact you clamp it in place with the head.
All alum. works of art like Pat's Shelby have these cast in place and are not intended to be replaced like say my JP-1 that uses a liner or steel sleeve. You can cut old sleeve out of Pat's block and increase size or bore ( I think 4.375 is max to yield 526 inches ). The catch is a lot of special reinforcement has been done to block to allow these bores. The Shelby is a work of art with 3 massive ribs in valley and a very thick deck so it does not move around.
We change liners in the funny motor all the time as needed but is a $$$ block also. I have run several factory alum. blocks, all have sleeves installed so rings are on steel not the alum of the block but these are cast into block. I ran a 215 and 225 with 25 pounds of boost in a sand rail. What a hoot to drive.
You do not need to weld or braze sleeve in block it relys on crush / clamping on top and a bunch of locktight. My JP-1 uses o-rings on the linner but is a dry block. My Cummins uses shims and o-rings for a wet block.