I can't speak for Summit brand converters but I did buy a Jegs brand 9 inch converter (4500-48000 rpm)
I ran it for 2 years zero problems behind a fairly stout BBC 468.
If I remember correctly I paid around $300 for it.
Now I run and swear by Transmission Specialities (T/S) 8 inch spragless converters. Kinda pricey though, around $1000 to your door.
Cp