with a 1948 3/4 ton chevy truck with a rebuilt (30,000 miles ago)250 cu in chevy engine with standard 4spd tranny and 4.56 rear end , (rebuilt brakes, shocks and sway bar etc) and 16inch radials, what is the rpm that is safe to run. I have calculated that at 5o mph the rpm is 2556, at 55mph 2811rpm, at 60mph 3067 rpm and at 65mph 3322rpm (i don't have a tach). there is info on this forum regarding the 235 but not much on a 250. I don't think I want to change my driveline and know that mpg goes down as rpm increases. I get about 12 mpg at 50 t0 55 . I guess the question is whether it is a good idea to run it above 55mph for very long thanks for all the help
