What mods for my 904 when using the BPE 408?

I will be replacing the tired, smokey, original 273 in my 1967 Barracuda #projectvertfish with a fresh BPE 408.
Since it wont ship until mid October 2020, I have some time to freshen up, build up, and modify my 904 TF transmission to hopefully handle the 500-ish HP.
What mods can you recommend and what torque converter should I get?
Thanks in advance.

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