They were using factory sleeved engines, not adding one to a cool-bore. Yes, you can have a sleeve installed in a worn block, but the cost likely outweighs the value. You'd have to really love that block to not just find a nicer one. Oversized pistons are around for most, and as long as the finish is done correctly, should live a long and happy life. Upgrading to a more modern piston design would be nice. Millennium can Nikasil the bore, and make up for a reasonable amount of wear. Harder than woodpecker lips and still good heat transfer.