First thing first..... If you want to make say 750-800 rwhp with a turbo/turbos, there is no reason to build a motor that big..... You could easily make enough power to break the 69 block with a 357, this will solve any compression issues..... Also I would seriously consider 1 decent size turbo rather then 2 smaller ones, you can make big powa with one in the 80mm range..... Just look at Wendy's car, it has an 80mm/363 combo that currantly makes 750 on relatively low boost and there still tuning.....