My dad ran 9.59 best with a factory 4 bolt block and a stock reground crank, in my dragster an 8.59 best. IMO factory cranks are better than the China cast crap most are selling now. External is fine for a factory crank, don't use a Fluidamper with it. If you are buying new, Callies has some inexpensive steel cranks and are worth paying the difference for. Their machine work is excellent. While it can be done, going more than 3.75 stroke is a pain without a raised cam block. Also the factory 400 rods are fine with ARP bolts, resized and magnifluxed. Ran as fast as 10.90's and never broke one. For your app the factory stuff will work fine.