a while back i bought a 68 camaro superstock car 70s era had been sitting for years the owner gave us the motor in pieces all fresh, and the first thing i noticed was it had 8 sleeves!!!! i talked to my engine builder and he said some guys like to sleeve the cyls to have perfect sealing that you do not always get with a non sleeved block, i have ran sleeves before and if it is done correctly it will be just fine, the bottom of the sleeve should be stepped to the cyl.