Clean up port I'd run the small bores.. As far as BB's adding 10HP.. Thats bull shit.. The big bores dont add any hp over the small bores (on a 421 application atleast).. Just more power on the bottom and mid without losing any top. If it does add any peak hp.. it will be very minimal....
I used Big bore shearers on my Drag ported 421, But every motor and every builders port work is different and inturn will favor different pipes.