I wouldn't be comfortable having to grind that much off the housing. How long has this guy been driving with it (aggressively)? Any problems?
1999 BMW E46 328Ci TS2
1992 BMW E36 316i Sold
1987 Suzuki VS1400
1996 Suzuki LS650 Sold
1984 Kawasaki 305CSR RIP
Went from 305cc > 650cc > 1400cc > 2800cc
No prizes for guessing what my next engine will be...