I'd probably step back to one of the 204/214 @ .050 cams Summit has for a 305 with an automatic, unless you plan on running an aftermarket converter with a higher stall, it will still be an aggressive sounding cam for a 305. The power gain you'd see with the larger cam would mostly be over 5500 RPM, which you'd spend very little time at running on the street. The loss of torque on the little 305 would probably slow it down. Whatever cam you pick make sure you have enough valve spring to accomidate the lift.
