42RH rebuild / update options

I could use some advice on what my best options are for upgrading a 42RH transmission.
It's going to go behind a 318 Poly with Edelbrock four barrel producing about 250HP. I'm looking for smooth changes and reliability rather than raw power handling for burn-outs.

There seem to be several options of differing numbers and angle of planetary gears, stronger and wider brake bands, mods to make pump work in park etc. Also beefing up the overdrive or swapping for a later 46RH overdrive. Is the 5 plate clutch a must-have?

I don't want to overdo it or spend where I don't need to. Just adopt any good modifications that deal with classic weaknesses.

Any suggestions very welcome.