Taming the shift on my trans

Ok. I bought a core transmission for a good price. I'm thinking of rebuilding it myself. Keeping the throttle pressure. Maybe a shift kit. Any recommendations for a rebuild kit with all the parts included (not shift kit parts). Also, should I use a bolt in sprag? Who makes a good one? What about pressing the bushings in properly?
Car has a 440+.030, .515 Hughes cam. 750 race Demon, RPM intake, 3600 pound car, with 3.91 locker. Ran a best of 12.12@110.
I want to keep the performance, and to be able to manual shift when I want, but automatic when cruising.
Most of the time the bushings are Ok. For-sure get a shift kit, and probably a governor kit.