Stock sohc engines can hold decent power with stock sleeves. Rods and pistons are the weak point and if it's well tuned with NO detonation, the sleeves should be good to go. Most people that want to boost the crap out of something here, on pump gas will likely kill a piston before shifting a sleeve anyways.
If he is serious and wants to definitely sleeve... he can just buy a sleeved block from the US or PR. Trying one locally is not out of the question eh, but a shifted sleeve almost always means you would have to scrap A LOT of parts to recover from the damage... pistons, rods, crank and sometimes even the head can suffer irrepairable damage. I do know that people are running locally re-sleeved blocks and likely some of them are tuners.... they just don't want to let people know they are sleeved or built...
