I think you need to call or email Mike for any type of price involved with what you need.
He knows a lot about these six cylinders.
His 250's on his dragster with his cyl. heads make 700 HP each ,no turbo,blower, no nitrous.
Could you post some pictures on this forum(like your car) of some turbocharged Chevy 250's. They are not too popular here in the states.
Thanks
Hank