https://www.hughesperformance.com/street-strip-trans/
The only way you know for sure with a used unit is to install it .
You don't need 'Kevlar' bands or clutches. IMO
650hp is nothing for a t400 trans. I would recommend Hughes Transmission.
I ran a stock used 350turbo for 4yrs. before it finally failed. With a 350hp 400 Pontiac and a 200 hp hit of nitrous.
Good luck.
Maybe Half-inch stud will chime in on this.