The steel/tool steel/titanium they're referring to are the retainers. You won't be winding this thing any, so I'd stick with steel.
I highly doubt any cam you choose will exceed the .570" lift that GM's (much cheaper) LS6 springs cover. Of Comp's two LSx truck grinds, the
larger (212/216, 115 LSA) has .520/.524" lift, which is well under that figure. If you're talking the 212/218
XFI grind, it's still .522/.529". Specifically which cam Comp recommends will dictate the springs you should use.
Check out the
instructions on the trunion upgrade and determine whether you want to do it or not. I believe there are vendors that sell upgraded rockers if you don't want to tackle it yourself. Is it necessary? Maybe, maybe not. But it sure beats
this.
Once you get your cam figured out, call Circle D or another of the converter companies. They'll help you more than we can with your converter choice. Just realize it's more labor-intensive than a cam or header install.
Speaking of headers, stick with 1 3/4" primaries. 1 7/8" isn't necessary until you start getting serious with your power level.