I mentioned my experience a couple times here.
"Somewhere in the upper 300hp range you are probably leaning your input splines. And at that level you would want a custom converter anyway."
On my trans rebuild this past fall my stock input shaft was replaced due to splines getting leaned. Catching them like that was fortunate, before prolonged condition caused a failure. So I knew I wanted to prevent needing a pallet full of input shafts between Mini and Slug, and I want a complete ready to go spare trans.