Your max rpm for your big block????

You're right on the restriction if you fully groove. However you can also make the grooves very small, or only partially groove them. As you've talked about running the HV pump the extra volume "shouldn't" be a problem assuming the pickup side isnt a big hinderence. If you're running a quality spring I don't believe you need to worry about cooling them. You are talking about drag racing, correct? Or are you planning to road race this thing for extended time at these rpms?