[*Cobber*]

I have made stainless re packable side pipes for my car and although they get hot they also cool fairly quick too. I would doubt there is any noticeable difference in heat transfer or retention at exhaust temps between steel and S steel. When driving these cars it's pretty normal to linger around for a couple of minutes when you get out anyway so people can be warned of the hot pipes.

I agree a well designed under body system will yield better performance but in reality driven on the street these cars are not driven to ten tenths or anywhere near close.

Each to their own but to me the side pipes are a big part of a 427 replica, and if they are live all the better.