Swap or rebuild?

So if I can find a magnum that I have seen run or has a warranty try that. Otherwise work the heads and cam on my 318?:banghead: I know the 300 hp 318 threads, I guess I have never had any of my stuff on a dyno so I have hard time judging how much that is. I had a stock 340 swinger with a one step up cam in it, a 18# boost Shelby Daytona, and an SRT4. How would a 300hp or so 318 stack up against them?