Word I got from a couple old racers, is that with 403 or 455 top end, they run like a scalded dog.
I understand that the late production models were roller cam. I considered putting one in my 86 Camaro, when the 2.8 died. Having just spent $1200 on a reman trans, I just dropped a nice warranted crate 2.8 back in, instead. Last I heard, it was in the back of some guys shop, having cracked it's 2nd torque convertor snout. Apparently the tranny shop didn't do all the upgrades when it was rebuilt.
Anyhow, I figured a twin turbo 5.7 roller would be a pretty wicked mill, and stupid enough to make people wonder about my sanity.