A lot will depend on how hard and how often you're going to beat on it.
You don't want a manual valve body, so my suggestion is to put in a Transgo TF-2 shift kit in it. Probably the best kit for it.
Parts wise, if you're beating on it on a regular basis go with Alto red friction plates and Kolene steel plates. Otherwise, if it was mine, I'd use Raybestos waffle friction plates and normal steels. This setup seemed to work behind the 440's and hemi's quite well. Continuing on, new bushings, new washers, HD sprag race, new rear band, and the high energy flex band that is used in the A518/618 transmissions. Replace the rear clutch return spring and the rear clutch plastic piston spacer. The spring is prone to cracking and the spacer just for good measure. Both Superior and Sonnax make a new reverse servo piston so replace the factory one. I'd look closely at the output shaft ball bearing and maybe to be on the safe side, just replace it. Don't fret about the overhaul gasket and seal kit, as no matter what is says on the packaging, there are only a couple of companies that actually make them. Check with Cope Transmissions and they should be able to set you up. Hope this helps.
