What Mueller said. This engine should fit nicely in a 914 - but I wouldn't bother going carb. Make a fatty exhaust and get your noise that way.
There are various aftermarket options available. Slight guess here, but here are the sensors.
On the end of the Cam shaft is a VR sensor that reads the CAM position. (on the right staring into the cam belt housing.)
On the end of the crank shaft (top) is a VR sensor that reads the crank position.
(this engine might not have the cam read). The sprocket that fires these is funny for subaru, and only certain ECUs are capable of dealing with it.
On the top, under the power steering pump ought to be a water temp sensor (on a pipe that comes out of the top of the engine) and an oil pressure switch. I think there is also a sensor that bitches when theres no water around.
These guys use Mass Air Flow sensors, so you will probably want to switch to MAP (pressure based) for which you will need to run a vac line or a sensor, and get an air temp sensor into the mix.
In the exhaust manifold somewhere you should have a 3 or 4 wire Oxygen sensor - this is used to tell the ECU about the mixture. (2 wires are heat, 1/2 are the actual sensor read w/ optional ground).
The other wiring is spark and injectors. I think that's all the sensorship you should have.
You could run this engine using a Megasquirt and 6-cylinder EDIS crankfire setup if you wanted to. I think you could also run the KitCarlson EMS (although I'm not sure if it has ports for 6 cyls), both of which are tunable from a laptop. Having an O2 sensor and no turbo will allow you to tune for stoch using the O2 sensor which can be handled in software on the MS (it will mostly tune itself).
Or you could buy something, which would probably take less time on your part.
You could do carbs, but you would probably need something to drive spark for you, which would end up being an ECU, so youd probably end up with FI functionality around anyway - you might as well use it. I would stick a big K&N cone filter on it - you ought to get great perf out of that and some headers, and some nice noises too.
Subaru motors rock.