Good point about the piston speed, if I were doing a low buck torque motor I would open up the bores about 1/2 a thou (.0005) to compenstae for the extra heat generated from the higher than normal piston speeds and then cam/port the motor to limit the motor to about a 4800-5000RPM power peak with a redline of about 5300-5500rpm. I'd also shorten the factory pressed pins about 1/2 inch to save about 50 grams. A 400 piston is about 80-90Grams lighter than the 440 and the skirt and ring supports are roughly the same, in terms of bobweight my combo on paper comes out a good bit lighter than a 440 Magnum and lots of those got spun to 6200-6500. But remember (and a lot of people don't realize this) the cylinder pressure stresses actually drop off as the VE plummeted with the old heads that were already spent, even though the Frictional HP losses continue to move upward with RPM. All in, I think a low buck 490 built this way could safely operate to 5500, but again you want to 'build-in' your rev (piston speed) limiters to minimize the potential for sealing losses, and building to make sure the VE drops off like a rock at a moderate RPM is really a good way to do that. The motor will continue to accelerate but the RATE of Acceleration drops off because the pumping efficiency is spent. I can think of a lot of apps where a motor like this could be a lot of fun on the street....but Like Clint Eastwood says "you gotta know your limitations!"