If there is any meat to the combustion area of the cylinder head? You could remove material kinda like when they CC heads.
Pistons could also be fly cut to remove material but at what expense IE: blowing a hole in the top of the piston.
The engine would not produce much power down low till the boost came up,,maybe some web pages on tractor pullers might be a good place to look,,,those diesel powered pullers make some insane boost with 4 or more turbo's /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif