It's never a good idea to sleeve all 8 bores, you will get cracks on the deck between the sleeves after a few heat cycles and the block will leak at the deck surface. The only way to do it would be to keep the OD of the sleeves almost the same diameter as the existing bore, and go to a smaller bore like a 390 or maybe a 428 bore.
Depending on where the thin spots are, you might just consider going up to 60 over and running it as is. The 492" FE dyno mule used in my book was a 60 over sideoiler block; one bore had a thin spot of 0.079", and another had a couple thin spots of 0.086", and it made 675 HP on the dyno and was flogged mercilessly during my intake testing. It all depends on where the thin spots are. Major and minor thrust surfaces are bad places for thin spots (especially major thrust surfaces), but the front and rear of the cylinders are much less critical. Further, the lower the thin spot in the bore, the less of an issue it will be. Also don't forget that factory 427 bores have a cloverleafed shape outline, so they are thicker at 45 degrees, 135, 225, and 315. This helps with the strength of the bores.
The sonic map of the 427 sideoiler block used for my dyno mule is in my book, if you have a copy.