If the cylinder walls on the block off the A-4 are still thick enough, convert it to a coolant
system with a heat exchanger
. Running cold (140 degrees) as recommended for salt water
causes most of the grief of sticky valves, poor compression
Set to run at 180 degrees, the carb can be leaned out and the little A-4 will give about the same economy as most of the small diesels for a lot less money
. Yes, you will have to tinker from time to time.
If you do go to solid state ignition you still must carry complete spare ignition parts including another solid state unit or points and condenser. Easier to just run on points! Keep the timing set right and create a set of timing marks for your engine. Easier to set with a light than to mess around with twisting the distributor around each time you tinker with the points.
Adjustable main jet carb is the best if you know how to set it. If not, stick to the model 68.
Have the starter checked out by a good shop. This is one item that you probably won’t need to carry as a spare. The A-4 should start easily and the starter should last forever with new brushes
and lube once very ten years or so.