Swap or rebuild?

Thanks, we are doing the whole car. My boys are teenagers now so lots of extra muscle:D. Right now we are prepping the 8 3/4 rear and XHD springs, we will stay with the KH front discs. The 318 runs great but needs more power:burnout:. I guess when we pull the heads and see what it looks like I can decide how to do it. I am trying to decide if I would be ahead with a magnum or push the 318 more.