while my experience isn't precisely apples to apples, it's fairly close.
i have a 70 D300 dually with a flat bed, 383 2bbl 727 and that thing will straight *** burn all 4 tires unloaded, set you back in your seat at a roll on from 20mph and doesn't break a sweat on the fwy at 65~70 (unloaded).
my friend has a 73 D200 long box with a 360 2bbl 727 and it feels much more under powered even though it's a considerably lighter truck. it has gobs of torque and doesn't complain when loaded or pulling a trailer, but it fully adheres to the "it'll get there, eventually" adage.