Need advice on my 318

I agree with 318willrun, A low mileage Magnum is the best bang for the buck, factory long block including cam is said to dyno 320hp with headers. Add a some what of a decent cam and you'll get 1 hp per cid or more. Unless your looking for over 400 hp rebuilding ain't necessary and even then can be done on a stock short block with eddy heads.