I found this interesting site that calculates the TB size according to engine size/rpm/bore/stroke...etc...this helps determine the correct TB size for engine application, even takes into account if engine has tuned exhaust and cam.
Here's the link:
http://dairally.net/daihard/chas/Mis...8&Button=Reset
I know there is a lot of debate about the power gains, if any, on boring the TB to 79mm (like the Dinan TB). I also found this other site that explains the science behing TB size selection and why sometimes a bigger TB size doesn't yield any gains.
http://www.musclemustangfastfords.co...t/viewall.html
From what I've read, it looks like no one can label that 'x'mm increase in TB size will yield 'x' amount of net hp. The TB power gains depend more on the intake/exhaust CFM capacity, intake air pressure, cam timing and other factors.
Enjoy
