It depends on what you want the engine to do and how much you want to pay. If you want a race motor that's one thing but if you are mainly running on the road with occasional track use then that is another. I currently have a 302 with Edelbrock RPM top end which did 335hp and 340 torque on the rolling road. I am building up a 347ci with internal balance as this makes for a sweeter engine and also gives the centre main a much easier life. I have some "Chinese" heads but fitted with Manley valves, springs, guide plates etc. They are quite a bit cheaper than the Edelbrocks and are very "similar" to the Dart Pro One heads. A 347 stroker with Eagle internal balance kit, main girdle, and Edelbrock RPM heads, air gap manifold, 650 cfm double pumper Holley, road cam, gave 420hp and 430 torque. A GT40 with this engine was pretty quick too and road driving friendly. Get your block checked and machined up true by someone who has experience of these things. Get your engine run in and set up on the dyno before you fit it. Make sure your fuel system has the capacity to feed a 347 as a slight blockage on a barely adequate system can have the engine run lean with bad results.