I haven't done one, but just thinking about it, these issues come to mine.

Need complete fuel injection pump, governor, and its timing advance unit w/its gear and cover. (but you should take the time to research "timing" as your engine may use different pistons and nozzles and you would want a "used" fuel injection pump to have similar timing, that used those same pistons and nozzles)

Note: I believe most PEEC engine were 14 degrees base timing with electric advance unit that did "twice" the amount of timing verses the mechanical timing advance units. My guess is you might be able to use a mechanical fuel injection pump with 16 degree base timing or maybe even 18 degree base timing, IF the pistons and nozzles were the same, as your original PEEC engine. (looking up part numbers, is how you research this) Also, most fuel injection pump have their timing (in degrees) etched with an electric pencil, in the front end of the fuel injection pump camshaft (timing advance must be removed, to view) = this is good to know, if you go to a recycle yard to find a complete fuel system.

You would lose cruise control.

You would need to rewire jake brakes.

You need to install a mechanical throttle linkage, return spring and its bracket and accelerator foot pedal (in cab).

Get correct wires for the shutoff solenoid, wired.

Even if you got a complete unit, from a recycle yard, you still may want someone to go thru it, before installation = more $$$