I am considering this also. I really wish I would have done it when I built the car along with sub frame connectors and a mini tub... but had different goals then.

I am running Spitfires now but have a Shady Dell 408 coming in March. We are going to dyno it with the Spitfires and see how it does with them.

The Spitfires were reasonably priced but the custom exhaust work required to get them not to rub rattle and make the car fun to drive was not.

I have the TTI's on my 65 and the K frame fitment is good the T bars are the worse part, once the headers are in they fit good don't bang on anything and they flow great. When you install a big header in a small car its not always easy.