383 Engine questions

Hello guys, this is my first post, I have a 1975 Duster with a 416 that I have built for it, just so you know my background. If someone can give me some computer assistance I can get a pic of it on here for ya. But for my first post, I have a question about my C body. It is a 1967 newport custom with the original 383 4 bbl and only 89,000 original miles. I am going to rebuild it this winter, although it runs fine now, and get some more power out of it. I believe, as I know that many other people do as well, that there can be some good power gains out of the 383. I am looking for the area of 425-450 horse for my big cruiser, and equal torque. I will be installing 3.23 gears in the 8 3/4 and a 2300 stall converter i have on the shelf in the 727. I already have 2.5 inch dual exhaust all the way back off the manifolds with dynomax mufflers and will be installing the 1 7/8 TTI headers also. Now my question is, I believe my 383 has the 516 heads, instead of the 915 heads. Can these heads have larger valves installed, with bowl work and port work and work equally well as the more desireable 383 heads, or should I try to find some 906 heads or 915 heads? Also, what aluminum intake and hydraulic cam will work well with the 383? I am somewhat new to big blocks, as I have always had small blocks, and am looking for some ideas. As I plan on using the original rods and crank, please no suggestions about stroker kits or edelbrock heads, as I am wanting to keep the car relatively original looking, minus the headers intake and carb, and not spend a boatload of money like i did in the 416, lol. I appreciate the advice and sorry about the long post

-Will-