Good news parts are easier to get than you think.
Crane cams, comp cams, crower, clifford performance and paw performance have camshafts for the 300. I would focus on crower and comp cams but thats my opinion.
Crane cams, comp cams and clifford can get you a set of roller rockers.
Carbed intakes your limited to offenhauser C or DP and clifford performance has a few to choose from but cost a fair bit more. Unless you wanna cut up a few stock manifolds and make a dual or triple carb setup.
Headers can be purchased from most of the popular header companies like hooker and heddman(not always listed but they have them just ask), clifford has them as well.
Stock rods are forged and fairly strong, the stock cranks are cast but again pretty strong as is.
Pistons aren't difficult to find either, 351w pistons can be used with a little work to the stock rods, if it comes to that.
Good luck
