The cam won`t have the same lope it has in a 350, 400`s swallow bigger cams somewhat. we were running a 234 244 duration cam in a 400 and it just had a noticeable lope. In some cases this acts as a advantage, if you get a race and don`t have to open the hood let the smoother idle work to your advantage, the old "hey it`s just a 350 with a little cam" works pretty good.
With Vortec heads it`ll have blow the tires off out of the hole power, but I`ve also seen first hand what one will do with 200cc runner heads and it was incredible, it came out of the hole like someone kicked it square in the a** and screamed throughout the rpm band, but then again, we used to take 1st place in the mud races often with a 400 that had a old set of ported camel hump heads, 400`s hump period with just minor mods. If you run vortecs, make sure you do everything you can to keep it cool, run vortecs hot one time and that`s it. And I`m sure you`ve already been reminded of the next 2 things but it needs repeating, if your running the stock 5.565 rods don`t get rev happy or they`ll come unglued, and make sure you have the steam holes drilled in the heads.