what to do with noisy engine

I'd like to get some opinions on what to do with my noisy engine.
I've got a '97 SE with 184,000 miles on the 4.0. I am pretty sure that there is a rod knocking in #4, #5 or #6. I can get an engine with 130k miles for $550 or have the crank turned, new brngs and gaskets for about $225. It runs really good as is and has alot of power. Was a state vehicle for the first 150k miles so I know the maintenance was good.

thanks

let it go till it blows.