which heads on a 318

I've begun a to compile a few pieces to upgrade my 318 & need some advice on which head actually is best for the goals I have in mind. Ultimately, I'd like to build a car with good throttle response, which sounds good at idle (read; more agressive than stock) which can still handle freeway speeds (70-75) at a reasonable RPM. Really just gonna cruise it with a little "spirited" driving thrown in however, I'd like to end up with a finished product making 300-320 HP. Here is what I've done & items on my wish list, i'm specifically interested in head choice at this point for my desired goal.

current upgrades:
Holley 600 cfm http://www.holley.com/0-80457S.asp
Edelbrock Peformer Intake http://www.summitracing.com/parts/EDL-2176/

Cams to consider:
Comp Cams 224/230 @.050 Dur 477/480 lift http://www.summitracing.com/parts/CCA-K20-223-3/

Summit Racing Cam 218/228 @.050 Dur 441 lift http://www.summitracing.com/parts/SUM-K6901/

Headers:
Doug's http://www.summitracing.com/parts/DOU-D453-R/


I'm unsure if the stock heads with this setup, bored exhuast valve to 1.60 will be my best bet. Or, if a 302 casting would be better due to swirled ports or even maybe a set of 360 heads like a 915 casting with the 1.88"/1.60" valves would help me reach the goals I have in mind. Thx for the feedback.