We extend to you a cordial "WELCOME ABOARD !" Come on in, make yourself at home, we are a friendly group of enthusiasts, and we also appreciate the classic Chris Craft Roamer, Corsair, and Lancer boats too , as they are all on the same family tree and share much in common !
Those engines will be very nice. I work with a number of OEM boatbuilders (Oh- when they used to build boats in the US that is) and the QSB series is really an excellent engine the common rail diesel really makes that 5.9L sound quiet and improves nearly every aspect of the performance. I know that these have a nice torque curve and this was my choice in my repower before I chickened out and used crusader 8.1L Gas. I still have the diesel envy but for my 35 I am very happy with my choice. I hear great things from many on these engines and I think you will love these engines
One thought is that on the CC hull many had fixed wedges that acted to help bring the bow down. If you add more power and thus prop lift you may find those wedges to be potentially a problem. I expected this may be the case on my 35 repower as I would get some bow steer on my 35 at about 30mph prior to repowering when the seas were a little rough. I decided to grind off the wedges with the idea of controlling any trim issues with trim tabs. I believe for my hull as configured it was the right choice because will adding about 310 HP and much more torque to my boat I seem to have eliminated the bow steer. My WOT speed is now just over 34 knots which is pretty good for an old boat. I feel that what improved my performance was the removal of the wedges and the addition of large external trim tabs. I don't really know much about the 42 hull but I know it is alleged to be similar to the 38 so just some food for thought as you embark on repowering that beautiful 42.