75 Penton 400 pipe question.

[TedG]

As I have mentioned before I am building a Flat Tracker out of a 75 Mint 400. I have reshaped the pipe into a downswept and have it down to the stinger. The problem is that the original pipe had some aftermarket silencer on it and the stinger was not original.
My question is does anyone here know what the inside diameter and how long the stinger was on the stock pipe?
Thanks in advance,
Ted