69 GTO 2.5" Vs. 3" Exhaust?

Hi,

I have a 69 GTO with a 400 engine and TH400 trans.  I currently have the frame off the car and have finished the front and rear suspension and brakes.  I would like to put the exhaust back on the frame while I have good access to it since the body is off.  Can anyone give me advice on whether to go with a 2.5” exhaust vs. a 3”?  If I increase the displacement of my 400 with a stroker kit would it be better to go with the larger exhaust?  My intention is to have a good driving car when the project is complete.  Any input would be appreciated.

Thanks,
Steve  

If the engine has 400H.P. or more then go with the 3" exhaust if less then 400 H.P. then go with the 2.5" exhaust.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Thanks for the quick reply.  I went with the 2.5".  I'm building a street car anyway.

Thanks again,
Steve  

Your welcome.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

I usually let displacement determine exhaust size 400 or larger can benefit with 3" using tailpipes-this will give you some room at bends or transitions if you don't have a mandrel bent system-of course the use of headers or manifolds is also a factor.Mild to wild There is a program with which you input all pertinent daa and it will spit out excellent proven exh. sysem suggestions-Exhaust technoligy is way beyond what it was 5,10,15 yrs ago
Learned the hard way-(muffler shopowner)have seen cars with turn downs run faster with the addition of tailpipes,go figure.Also more often than not the deletion of tail pipes increased top end-Since mytimeis now spenon the street I focus on bottom and mid range.