That's a tall ask on pump gas for even a stroked small block. Unless you plan on using an R3 block you are pushing the limits of a 340 at 700HP. Yes I know there are guys who have built them and drag them but they are all running race gas and a ton of nitrous. Even the Nascar P5 engine mentioned above runs on a combo of Ethanol and 98 octane so its not really a pump gas engine either. Based on the stroke and bore you are referencing then an R3 is the only block you could use, but your still looking at probably 11:1 comp ratio. Indy sells a 440 small block R3 crate motor running 10.25:1 that they rate at 600hp. Thats about as high comp ratio an iron head engine on pump gas can take reliably. It is possible however if you use E85 and aluminum heads you could bump that up to 11:1 or maybe even 11.5:1.