Power for a slant

I have a 64 Dart GT, just bought recently. The slant is pretty tired. I was thinking of swapping to a LA series V8, but now I wonder if it is possible to build a warmed up slant capable of, say, 200 hp and still retain a nice, smooth idle with good street performance. Don't intend to race it , but want a bit more than the stock slanty can give me.