Just put a smaller cam in it and maybe a smaller carb. We used a small roller cam in Tim's 427 small block with a 650 Holley carb. Sure it gave up some top end power, but it idles smooth at 800 rpm and still rips the snot out ya when you stomp on it.

The cam I used was about 20 degrees smaller than what the internet experts suggested. The carb was also a ton smaller than what people recommended. I knew that if I followed the normal advice I'd end up with a lumpy, peaky motor that fouled plugs and wasn't any fun to drive.