how much hp can a high milage 2jzge hold
 

a friend at work has a sc300 too but he has 19700 miles on his block he plans to turbo charge it , he has a t-66 turbo and a ssautochrome kit he wants to use gte metal gaskets and change injectors and fuel pump thats it i told him build the block but he said no i think its a bad idea what do u guys think ,others info might help me or maybe i dont know what im talking about!

one month with hard driving

It really depends on the condition of the other parts of the motor. If it's a well maintained motor, it might last with conservative boost. More than likely, the valvetrain is worn out and needs a refresh. Does the motor seem healthy at least?

For my NA-T project, i'm completely rebuilding the head to hopefully better than factory specs. I'm sure many people have gotten by with the whole ssautochrome+head gasket+arp headstuds and some random turbo...but i prefer to have piece of mind, and not a broken down lexus on the side of the road.