I towed a 6000 pound trailer for years with my 1976 Ford 500 sedan and less than 200 hp 351 and three speed auto without TC lock. I never felt underpowered, but never felt the competitive juices to beat the sportscars up the grades either.
Nowadays, I tote the same load with a 215 hp 1996 diesel. I don't go faster than my old 76 because I don't care to.
It's all a mind game.