Sankei is a company that manufactured exhaust for various Honda models and I believe they are still in business. I have a 4 into 1 model on my 550F, it is prolly the worst part on the bike! These mufflers tended to rust through.
If I remember correctly, the 405 model is for the '77-78 750 model. I had them on a K8, they were very restrictive and quiet, I didn't care for them.
I like the 341's much better