You are borderline on where I use the 36 element sprag and drum setup. You definitely want to use the hardened outer race either way.
You don't need fancy clutches, I would machine the direct apply piston for 5 frictions, use stock Borg Warner friction clutches, stock steels, dual feed the clutches internally, double up the sun gear bushings, drill the feed holes in the seperator plate and block the 2-3 accumulator. It will shift crisp at light throttle and firm at WOT and won't break parts.
I drill the feed holes to about .135" and retain all the checkballs.
If you want it to shift harder you can leave out most of the checkballs but I would definitely use the 36 element sprag/drum setup in that case.
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