Gentlemen -- I have a B-42S that I am looking to swap out the gasser and put in a diesel. I have a Detroit 671, which is simply to big, over 54 inches long. And while I could make it fit but cutting into the cab, the cab is small enough on it town without putting a doghouse in it. I now have a lead on trading my 671 for a Cummins 6BT. While the 6BT is right about the same size as the original gasser in terms of over all physical size, I just am going back and forth on if it will be powerful enough. I am looking for some over all suggestions to help get me pointed in the right direction. I will say that I am very new to dealing with Mack trucks and big diesels. I know that what I will be doing with the truck will determine the over all horsepower I'll need and such. The truck will be doing medium to light duty tasks. I will be putting a 20 foot flat bed on this truck, to haul some of my older vehicles, and towing from time to time a 24 foot enclosed trailer. I also know a lot will also depend on the transmissions and the gearing... A ton of "ifs"... But the cummins is a great deal for me, and from my research they used it in light duty and buses so it might be just what I need. But I thought I would come to the experts and find out what you think. Thank you for your time and help! --Josh