I was in the same boat last year. Had acquired a ton of used parts over the years. Over half of my parts turned out to be junk.
Z-bar with dougs or tti's require some fabrication. (Depending on what you have you can buy one that's suppose to work with these headers)
I would buy the Brewers rebuild kit after you take the transmission all apart (unless you know it was a functioning piece. Mine looked good but after torn down the main shaft was junk)
Steel shift forks are cheap insurance.
Make sure your crank is drilled for the pilot bushing. If not there is a couple different options.
Check your bearing retainer diameter/bell housing.
Remove over center spring with the center force diafram clutch.
Test reverse switch while the fluid is out.
If I had to do it over again I would have just bought most of the stuff from Brewers in the first place and been done with it. Great conpany to deal with.