If you want the radical sound and aren't concerned with overall performance, go with even more duration IMO, but be aware that even with the cam you're currently considering, a stock torque converter is a bad choice. You will be constantly on the brake and tweaking the carb to get it to idle when the vehicle is stopped in gear. With a 305, that cam will have even more problems on the stock torque converter than say a 350. Kevin is right with stepping back in that case, but your bad-boy idle will not be there.
Cheers,
MV
