261's were HP rated ar 3600 RPM, I believe, and I'm sure GM would not have used a speed that would damage the engine for rating the power output. A 235 or 261 with good oil pressure and proper bearing clearances will run all day at 3K RPM without any problems at all. Just for grins, try removing the fan and running a few miles at highway speed, and I believe you'll learn where most of the "engine noise" that people get concerned about is actually coming from. If you can come up with a gear ratio spread that allows the engine to have good torque in the 1800-2K range on an upshift, and pull strong to the the next gear change at around 3K RPM or slightly above, your 261 will be a happy camper for a long time.
Jerry
