Bill,
This is what I did for transducer mounting on my 268. It works very well and gives me the option to replace transducers in the future without drilling or patching more holes in the transom. The mounting board is "Starboard" material like a white nylon cutting board. It is very easy to cut and shape to fit. I pre-drilled the screw holes, coated the board with 3M 5200, and installed it.
viewtopic.php?f=3&t=14085&p=136057&hilit=transom+transducer+mount#p136057I've heard that you can connect the fuel flow sensor to the fuel pump end of the existing hose and add a short piece of fuel hose between fuel flow sensor and the fuel cell (fuel pump assembly). That way you can return the system to normal if the fuel flow sensor ever needs to be removed.
I have a Lowrance HDS 8 (Gen 1) Chart plotter/Sonar with StructureScan and the pre-loaded Lowrance mapping program. A touch screen would be nice, but we really like the unit. Removal involves disconnecting 3 electrical plugs and 2 mounting knob bolts. It takes 1/2 minute to remove. We remove ours every week.
Hope this helps.
Gary