Help on 198

I have a 70 dart that Im going to drive while I restore my 67 dart. ? is I have a found a super six set up at a pick n pull and was wondering would this motor benifit from it. My car has a new 2'' exhaust from head pipe back. Would milling the heads .090 give me a increase with this combo. i dont want to get to extreme with upgrades. What kind of increase in power from the super six and milling the heads give me?