The primaries are old school long. They were able to run that over size pipe because of the excessive length. That explanes the super low torque RPM. I would rather move the torque way higher to be more useful by shortening the primaries. This will move the peak HP higher. Unless you plan to blow NO2 at this engine the collector is way too big in dia. You are proving how a headder works by making the primarys longer you can make them larger and get a similar result as a proper sized shorter pipe will act. I prefer to size them for the shortest length so you can fit them in the car. If pipes you dynoed with fit your car well I would get a Merge collector from SPD in california to top them off for now and go have fun. My 582 Profiler headed 1205 HP 924# monster uses 2.375 to 2.5 total 25" long with 4.5 to 4.0" merge collector 12" long. Your conventional valve head will not move that much air as the profiler no matter what you do to them. Your Torque is crazy high unless some engine builder dynoed the motor for you then the # would be in question HIGHLY I might add. Sounds you have a decent set of pipes that seem to work well for you. Think what a nice set might do?
If I had to weld in New Zealand would I have to hold the tig rod in my other hand? (':lol:') Have fun in 09 and kick some but at the track!