I could be wrong here, but I understand unstamped mufflers are quite hard to find. It all depends on what sort of restoration you want to do! the original unstamped mufflers on my bike did not last 3 years without
#3 rotting out. My dad who first owned the bike replaced them with a set of 2 into 2 shorty drag pipes. I blame this for my consequent hearing loss due to tinnitus.

In effecting the restoration they were replaced with a stamped version.

Of personal interest here; One of the pipes we found was actually sitting in the local Honda dealership. I am suspicious that it was ordered for my dad who then ordered shortys for it after he discovered the price of the single pipe replacement. It then sat in the shop for all those years!  After obtaining the remaining three pipes, I can confirm this cost me more than my dad paid for the bike in total in 1970. I know this, as I still have the original bill of sale!   

Paul H.