Regardless of which engine you choose, 216, 235, or 261, the practical RPM limit of a stovebolt six is somewhat less than 3000 RPM. Simply making the displacement bigger isn't going to do much, if anything to increase the top speed. At 2500-3000 RPM, any of them is going to sound like it's over-revving. It's not. People are just too timid to run the engines the way they were designed. In the bigger trucks, stovebolts ran wide open, all day, every day, carrying loads that today's snowflakes with lace on their manties would never consider hauling in their pampered toys. Either figure out a way to switch to a 3.50-something rear end ratio, or find a 5 speed overdrive transmission to increase your road speed.
Jerry
