Theres a few good points here, but I have to ask a few questions. Why are you planning to attach a 150 shot of nitrous to a Big block motor? I guess if you plan to make a race motor, but what class do you plan to run in? There are rules to every class, such as displacement limits, induction, ect. Also, if you get into a series that allows it, a Blower/turbo is always an option. Granted, it gives away your game, but its always there. Finally, If your looking for higher R's, why not try a large-bore small block? Less work for higher R's. Just throwing it out there

Dave