Making rally muffler- What's the difference between a 3.0 muffler and 3.2 muffler?

[silver911rdb]

Hi,

I'm getting ready to make a rally style muffler (2in and 3 out). I know 2 local guys that have this style muffler made by Auto Associates. I've examined them both and see that they used a later 3.2L muffler part# 930.111.043.00. Does anyone know if there's a difference internally between and 1978 SC muffler part# 930.111.022.00 and a later 3.2 muffler part# 930.111.043.00? I'm really interested in pipe sizes and any other differences such as chamber locations and pipe routing. I currently have an early 2in/2out and also an SC muffler that I could use as a donor. I'm wondering if the reason they used the later 3.2 muffler was because of larger internal pipes. If that's the case I should probably start with the later 3.2 muffler.
Also, if anyone has any input as far as internal baffling changes that need to be made I'm all ears. My goal is to make a muffler that is quiet enough to run at Lime Rock (accomplished by capping the 2 rear outlets and running a single side outlet) & also be able to run unmuffled at tracks like Watkins Glen by simply uncapping the 2 rear outlets. One of the mufflers I inspected was the one mounted on Tom Butlers car. What a beautiful car!

Here's a picture of what I'm trying to build

[175K911]

One difference between an SC and a Carrera muffler is the indentations in the case itself. The Carrera muffler has a long crease in it to allow the heater crossover tube to go from left to right. And the Carrera muffler has an indentation in the area where the hanger off the back of the engine fits in place, the Carrera hanger is a different shape so the indentation in the Carrera muffler is deeper than an SC. So the bottom line- a Carrera muffler will fit on an SC, but an SC won't fit a Carrera without modifications with a big hammer.