As has been said already, heads would get you the most power, but would be $$.
Bang for the buck? I would go with a 4.5" crank and 7.1" rod. More power especially at shift recovery, lighter bobweight, and not much $ when you sell your old stuff.
Plus would be a better foundation when you finally upgrade your heads.
I agree that would be great to get a rew more cubes.
My current crank is a Crower center wieghted piece , replacement cost over $2500, best steel short of billet (en30b?) Rods are 849 gram hbeam 2.200 journals, so not a lot to gain? Since i am going aluminum block that center wieghted crank may aid in less cylinder distortion and better ring seal.
Didn't realize you had a high-end crank, I wouldn't replace it with standard 4.5" stroker.
Now I'm thinking 4.625" center counter weight rotating assembly, hard to find and expensive, but still cheaper than heads.
you are at the point (as I'm sure your realizing) that any gain in ET is going to be expensive. I don't think better piston and rings are going to get you there. Start thinking about future upgrades, more cubes make more power under the curve, easier on the valve train, less sensitive on matching the convertor, etc.
