I agree with most everything said here. You will make over 1000HP easily, just up in the RPM range, 8000 and above. Volumetric efficiency is everything and I don't have my dyno sheets available right now but would be willing to share what my stuff has done in the past. The guys that are building your engine are top drawer from everyone I know that build high end engines so listen to them as pointed out. I would think for a land speed application that merge collectors would be a waste of money but you also know people that would know. Most of us on this site are drag racers and that's a totally different dynamic than having a few miles to get up to speed. I'm thinking with the right tune up, you will break records.