Since no one has answered, ill take a shot. You might be better off at a place like powerstroke dot org.
I know the 365 is more reliable than the 6.0, mostly due to emissions equipment missing in certain years. If it has an EGR cooler, then do be careful with upgrades. The stock Ford heads work, but aren't that impressive. Really most of it depends on the year and what the 365 is already equipped with.
Beyond that, I wouldn't do much more than a tuner, making sure to stay within the limits of the different modes. Bill Hewitt at powerstroke specialty in Atlanta has some nice aftermarket heads, then you can tune up an mod a bit more.
As far as exhaust brake, I would suggest a ford diesel forum