The first all out custom built drag race 8.0 inch converter I was involved with was from Art Carr, it slowed the 1968 hemi GTX down right at .3 ET and 3 to 4 MPH in the 1/4 mile from the stock 11.0 inch street Hemi converter, his was a real piece of chit
We, I, took it back 4 times for him to fix it(it had broke on the second run the first time we got it ) and I think he finally swap another one of his customers 069J B&M converter with us That picked the car up around .4 ET and didn't lose much MPH from the stock OEM 11 inch Street Hemi converter
I've had other horrible race converters from companies like Art Carr, GER and some other I won't add onto this now.
My main message is a good converter is absolutely needed for the car to 60 Ft. and MPH well