Can a 383 get me to low 11's or high tens without nitrous or turbo/charger?
You'll need a pretty radical cam to get to low 11s or high 10s with the 383, but it can definitely be done. I think that the issue that you'll have with a $2000 budget is that you will be running a mismatched combo throughout your build. That is, once you get into the top end and build it for a radical 383, it would be mismatched with the stock bottom end. The previous suggestion of headers was a good one, but once you have spent your money on the simple bolt ons, you might want to consider tucking away 2 years of money for the rebuild and do both the top and bottom end at the same time. Also, don't forget, you'll need a good set of heads since you have the stock iron 85 heads, so what you'll quickly notice is that these costs add up very quickly.