Race blocks

Now that I've jumped into the pool and learned a little about the world of Mopar performance, I'm in the very early planning stages of the next motor for my Duster. I am sticking by my chiselled in stone rules and two of the biggest ones is the car keeps a flat hood an air cleaner and no power adders. I want to go way up on power as in 700 plus so it is a tall order to fill. I have two more 440 blocks, and one 400 block. I'm really thinking the low deck B motor makes sense because I can go with a bigger intake than the Torker II I am running now. I also know about the limitations of the factory blocks so I am thinking on spending the money on a race block before I buy any other parts. I have been poking around the web and have yet to see any low deck race blocks. My first choice would be a 4.5 siamese bore iron block but I would also settle for a 4.375 bore if that's all that is available. Does anyone have info on this?