as for your point of 8.0 in a motorcycle it has been done. its called the tomahawak. viper v10 in a bike
the cylinderwalls arent the issue bud. The LS motors arent hondas you dont have to worry about stock cylinder walls and boost. The issue becomes head thickness and only 4 bolt heads. Production GM blocks have seen over 1500hp, many see 900-1000 hp easy