Inliners International Forums General Discussion Engines Weight of assembled L6 engines . . . .

Complete Book of Engine Swapping, by LeRoi Tex Smith, copyright 1968 might be the Hot Rod Magazine Technical Library book you remember. It shows the weight of a 250 at 475 lbs. Measurements are also given. Complete Book of Engine Swapping No. 2, copyright 1969 doesn't have that information but does have good info on swapping sixes.