Danger, Will Robinson! Eight sleeves in a stock block is asking for trouble. Typical failure is a crack between the bores at the deck, because after boring oversize for the sleeve there is not enough material between them at the deck anymore. They crack with heat cycles and then leak coolant. Been there, done that, and seen other people do it to. Wes tried this on his Poor Man's 427 and I believe he had the same issue, although maybe he will chime in here on it.
Furnace brazing may solve this problem although I don't know of anyone who has put a significant number of street miles on a furnace brazed block. I think those were mostly for race only applications.
A single sleeve, or multiple sleeves that are not next to each other, will be just fine, and last forever. Just my opinion, but as a general rule of thumb, use the thinner sleeve sizes, and never sleeve two adjacent bores.