what makes you think you need packing. I have gutted plenty of stock mufflers and after market ones and none have packing. Back in the day there were a few that did but that was not many either.
Packing is for making the muffler really quiet. Packing isn't even use much in cars except for the ones that are trying to get a deep tone but never really do.
You have a ton of holes that should make the pipes quiet. Parable to many holes. Have you ever gone and looked at baffles for pipes.
I thought you had thrush glass pack mufflers what was wrong with them.
Keep in mind you will never get the same sound as a harley never.
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