Yes there is no reason why not! A Temp gauge is as important for a air cooled engine as it is a water cooled one. So how do we do it.
1.Air temp gauge. If you look at the digital gauges you will find a digital temp gauge with a probe sensor. You drill a 5mm hole in the tin ware surrounding your engine, insert the tip of the probe and bond it in with epoxy.
​2. Think outside the box.  Fit an oil temperature sensor and gauge. The only difference between a oil temp and a water temp gauge is ........NONE! So use the sump plug to mount your sensor do the wiring and, jobs done!

These fittings are great for adding a temperature or pressure gauge to an engine that does not have a tapping in it.
Fitting:
You order the correct size of fitting for the flexible rubber pipe on your engine. The size quoted on the fitting is the flange size not the flat behind the flange. So if you need a really 'snug' fit order 2 mm smaller than the internal dimension of your pipe.
Cut into the flexi hose. 
Pass the supplied screw clips over the flexi pipe.
Push the fitting into the open ends of the flexi pipe. A smear of washing up liquid will help it slip in.
Pinch up the screw clips. Be careful not to go too tight to begin with, you can always tighten up if you need to.
Screw in the temperature sender, you will want put some PTFE tape on the treads first. Sensors come in all fitting sizes. You will find that if you need to change the size there is plenty of meat on this fitting so you can drill and tap it to match your fitting.
The last job that you need to do is run a negative wire back to the battery.
​Then you should be good to go.

Electricity is funny stuff described by Volts, Amps, Ohms and the like.
We don't describe fuses by their Volt value we describe them by their Amp value. 
So any 12 volt fuses, fuse holders, cable, crimp fixtures will work quite happily at 24 volts.  
​Try not to use 240 volt cable or switches at 12 volt as they may not be up to the job.

This is a very good question that people do not ask often enough!
Lets try to answer this by using an example.
I have a switch panel with five 16 amp switches on it. The switch panel has a single fuse fitted with a 15 amp fuse.
On one of the switches I have a LED Map lamp drawing 0.5 amps.
The next switch has my LED Nav lamps drawing 0.5 amps
The next switch has my VHF radio which is 5 amps
My cabin LED lights are 1 amp on the next switch.
And my Wheel house LED lamps take 0.5 amps.

The 15 amp fuse supplied on the panel by Dragon is there to protect the switches. But we are only using 7.5 amps so our 15 amp fuse is far too much for the job.
Lots of people would be happy with this as it gives is a good 'safety margin'. 
This is the wrong way to look a fuses. If a fuse blows that is a good thing - inconvenient but good.
In this case we should fit a 7.5 amp fuse (if we can get one) and it would not blow! Fuses have a 10% to 15% margin built into them and the manufacturer of all out electrical goods will have been given a maximum value so we probably will not be using 7.5 amps with everything on at the same time. 
The real thing that we want to prevent is fire! Electrical fire will happen when a electrical device or its wiring 'burns out'. So your fuse needs to be smaller than the burn out value of the device or wiring ( this is why your Dragon panel will have 25 amp wire and 15 amp fuse for 16 amp switches).

So in the case above even 7.5 amp fuse is not small enough. Our Map lamp above rated at 0.5 amp will probably only have 3 amp wiring running to it. So if the lamp burns out or the wire rubs through and short circuits, the wire will burn out before the fuse blows.

Think about your home circuits you have:
15 amp fuses serving many 13 amp sockets (UK values).
Each device will have its own fuse to protect it and its wiring.

So some in line fuse holders with one amp fuses sound like a good idea.

The short answer is yes - but there is a long answer.
Below you will see three pictures:
Top - a sensor that runs a warning light and a gauge.
Middle - a sensor that runs a warning light only.
Bottom - a sensor supplied with a Gauge that is matched to it.
The sender fitted intended to drive a light will not drive a gauge. so this gives you two options.
1 Purchase a gauge AND a matched sensor that will drive both your existing lamp and your new gauge and replace the original engine sensor with the new one.
2 Purchase a gauge AND a matched sensor and replace the original engine sensor with the new one.

If your engine is modern (post 2006) and has direct injection it is unlikely to have a heater system to start the engine.The engine control unit (ECU) takes over once you press the start button in your car and a few seconds latter the engine starts itself. 
Most boat diesel engines are vehicle derived but if its a 'home' conversion the ECU remains on the car/van.
These engines MAY need the diesel system pressurizing to purge the system of air/moisture before the engine turns over.
That is what the diesel prime function does on a Dragon panel. Once you turn the ignition on the diesel pump live is activated and the start function is not allowed to work for ten seconds. So your diesel is up to pressure and all air/moisture should be gone from the system before the engine turns over.

VDO Gauges do not come with wiring instructions, so......
The two large poles are used to hold the 'U' clamp that keeps the gauge in position and do not have any wiring attached to them.
The small pole that has a 'G' next to it is there so that you can attach the wire that is being run to the sender. Remember that the sender must also have a wire running back to negative on your battery. This could be the earth strap on your engine if it runs back to the battery.
The small pole that has a '+' next to it needs a (12 volt or 24 volt depending on gauge type) live feed from a switch and fuse. The gauge will draw 1.25 amp max.
The small pole that has a '-' next to it returns to your battery.
The red wire provides power to the gauge internal lamp. This requires 12V feed from a switch and fuse and will consume 0.05 amps when running. 
Please note there is no wiring for the internal lamp negative. there is internal wiring that takes that to the correct pole.
Please note. The Battery gauge - Volt gauge (12 or 24 volt) will only have two poles, so no 'G' pole.