Extrude hone exhaust manifolds

I have a friend of mine with a 1969 396 ss chevelle for whom I helped rebuild the engine. Eng is .030 over hyper pistons, open chamber heads, cam crane 272 216/228 .515/.510. Cast iron intake, rochester, 342 gears, 2500 converter, and American thunder 2.5 inch flowmaster header back exhaust with H pipe. The engine is not numbers matching and currently he is running small tube headers. He would like to put the stock exahust mainfolds back on for a stock appearance as he is going to be showing the car. He is worried about performance loss so I suggested extrude honing. I don't know who does this but I do know it is quite expensive. Money is probably not a restriction to him. I advised that there will still be a performance loss no matter what compared to the use of headers. Does anyone have an idea of the loss and who provides honing services? I'm thinking that because this is only a street motor with about 9 to 1 compression and the small cam that it won't lose as much torque or horsepower as say somthing more built. thankyou.

it sounds like ot would work, only problem is I drove by extrudehone the other day and the building was boarded up and for sale. Not sure how many other places are doing it.
Mark

fill them with acid they are thin to start with your not going to see any thing or much after the ex hone . it has more to do with the log mainfolds Vs a set of long tube headers

thanks for the replies. I'll let him know